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For more in-depth explanations, examples, and exercises, see The Ultimate Guide to SAT Grammar and The Complete Guide to ACT English. Full-length practice tests can be found in The Ultimate Guide to SAT Grammar Workbook.

Punctuation

I. APOSTROPHES

Apostrophes make nouns possessive.

For singular nouns, always add apostrophe + -s

The boy’s ball = The ball belonging to the boy

The dress’s buttons = The buttons on the dress

For plural nouns, always add -s + apostrophe, or -es + apostrophe if the singular version ends in -s (e.g. dress).

BUT if the plural form of a noun does not end in -s (e.g. feet, children, geese), then add apostrophe + -s only.

The boys’ ball = The ball belonging to the boys

The dresses’ buttons = The buttons on the dresses

The children’s game = The game the children are playing.

Pronouns: no apostrophe = possessive

It’s vs. Its

It’s = It is

Its = Possessive form of it

Its’/Its’s = Do not exist



Note: when the ACT tests it’s vs. its, the answer is virtually always its because that is the version students tend to have the most difficulty using correctly.

Incorrect: London is a city known for it’s (it is) many tourist attractions.

Correct: London is a city known for its many tourist attractions.

Incorrect: London is a popular tourist attraction; in fact, its among the most visited cities in the world.

Correct: London is a popular tourist attraction; in fact, it’s among the most visited cities in the world.

They’re vs. Their vs. There

They’re = they are

Their = possessive form of they; plural of its

There = a place

They’re

Correct: London and Paris are two of the most famous cities and Europe, and they’re (they are) known for having many tourist attractions.

Their

Correct: London and Paris, two of the most famous cities in Europe, are known for their many tourist attractions.

There

Correct: In the nineteenth century, Paris was considered the capital of the art world because so many famous painters lived and worked there.

Who’s vs. Whose

Who’s = Who is

Correct: Barbara McClintock is a scientist who’s (who is) best known for her discovery of “jumping” genes.

Whose = Possessive of who

Correct: Barbara McClintock is a scientist whose discovery of “jumping” genes helped earn her the 1983 Nobel Prize in Physiology or Medicine.

Note that whose, unlike who, can be used for both people and things/places.

Correct: London is a city whose many museums, palaces, and monuments make it a popular tourist destination.



II. SEMICOLONS & PERIODS

Semicolon = Period

Semicolons and periods are used:

1. Between two complete sentences

London is an old city; it has many new buildings.

2. Before conjunctive adverbs such as however and moreover when they are used to begin a clause

London is an old city; however, it has many new buildings.

London is an old city; therefore, it has buildings from many different eras.

Note: ACT grammar questions testing however use a semicolon in the correct version, whereas rhetoric questions use a period.

Important: make sure to read through every sentence all the way through to the period! Otherwise, you might not notice when there are two sentences. In particular, watch out for “sentence boundary” questions, in which the beginning of one sentence appears to be part of the previous sentence. If you don’t read far enough, you might think the sentence is fine as is.

Incorrect: Barbara McClintock is a scientist whose discovery of “jumping” genes helped earn her the Nobel Prize in 1983, she won the award in Physiology or Medicine.

Correct: Barbara McClintock is a scientist whose discovery of “jumping” genes helped earn her the Nobel Prize. In 1983, she won the award in Physiology or Medicine.



III. COMMAS

Commas should be used:

1. Before a coordinating conjunction to join two full sentences

Coordinating Conjunctions, aka FANBOYS: For, And, Nor, But, Or, Yet, So

And and but are the two most popular conjunctions; so and yet appear rarely, and or and nor almost never do.

Correct: London is a very old city, but some parts of it are extremely modern.

Correct: London is a very old city, and it is very appealing to tourists as a result.

2. Between a dependent clause and an independent clause when the dependent clause comes first.

Dependent clauses are clauses that cannot stand on their own as full sentences. They begin with subordinating conjunctions such as because, when, until, unless, since, before, and after.

Dependent Clauses:

Because I went home

After we returned from the movie

When we visited Chicago

A dependent clause can be placed either before or after an independent clause to form a complete sentence.

In the following sentences, the dependent clause is in bold.

Correct: Because London is a very old city, it has buildings from many different eras.

Correct: London was founded around 50 A.D. when the Romans settled on the banks of the Tiber.

3. Around non-essential words and phrases

A non-essential clause is simply a clause that can be removed from a sentence without affecting its essential meaning. When the information between the commas is crossed out, the sentence still makes grammatical sense. Non-essential clauses are always surrounded by commas.

Incorrect: London which is a very old city, has some extremely modern parts.

Incorrect: London, which is a very old city has some extremely modern parts.

Correct: London, which is a very old city, has some extremely modern parts. (London…has some extremely modern parts.)

The same goes for single words:

Incorrect: London is a very old city. It does however, have some very modern parts.

Incorrect: London is a very old city. It does however, have some very modern parts.

Correct: London is a very old city. It does, however, have some very modern parts.

Note: names and titles with commas around them should be treated like any other non-essential clause. Simply cross out the name or title, and see whether the sentence makes sense in context without the name or title.

4. To separate items in a list

Note that the comma before the word and is optional. As a result, you will not be tested on this usage.

Correct: Hiking, skiing, and white-water rafting have always been some of my favorite activities.

Correct: Hiking, skiing and white-water rafting have always been some of my favorite activities.

5. To separate adjectives whose order could be reversed

Correct: The groaning, rumbling train finally pulled into the station

Correct: The rumbling, groaning train finally pulled into the station

Note: Commas should also be used after introductory words or phrases (e.g. however, in the beginning, as a result), but this usage is not normally tested. Questions involving these words/phrases normally test meaning rather than grammar and include the commas.

Commas should NOT be used:

1. Between two full sentences (independent clauses)

When two stand-alone sentences are joined by a comma, the result is known as a comma splice. Comma splices are always incorrect.

Tip-off: comma + pronoun (it, they, s/he, one, you, I)

Incorrect: London is a very old city, it has some extremely modern parts.

Correct: London is a very old city. It has some extremely modern parts.

Correct: London is a very old city; it has some extremely modern parts.

2. Between two clauses with the same subject when the subject is not repeated

Incorrect: London is a very old city, but has many modern buildings.

Correct: London is a very old city but has many modern buildings.

As a shortcut, you can also think of it this way: because “comma + and/but” = period, plug in a period in place of the “comma + and/but.” If you have two sentences, the comma is fine. If you don’t have two sentences, the comma should be removed. For example, the incorrect version above could be rewritten as follows: London is a very old city. Has many modern buildings. That is not correct, so no comma is necessary.

3. Between Subjects and Verbs

No comma should be used even when the subject is very long.

Incorrect: The oldest surviving bridge in London, is Richmond Bridge, which was completed in 1777.

Correct: The oldest surviving bridge in London is Richmond Bridge, which was completed in 1777.

4. Between Compound Elements (Nouns, verbs, adjectives, etc. linked by and)

Incorrect: Many tourists travel to London and Paris to visit museums, and monuments.

Correct: Many tourists travel to London and Paris to visit museums and monuments.

If you have difficulty thinking in terms of subjects and object, think of the rule this way: “comma + and = period,” so fill in a period and see whether there are two sentences. E.g. “Many tourists visit London and Paris to visit museums. Monuments.” Clearly, there are not two sentences, so no comma is needed.

5. Before or After a Preposition

Most common prepositions: of, to, by, from, about, with, in, on, at

Incorrect: Frida Kahlo is among the most famous artists, of Latin American origin.

Incorrect: Frida Kahlo is among the most famous artists of, Latin American origin.

Correct: Frida Kahlo is among the most famous artists of Latin American origin.

6. Before or after the word “that”

Incorrect: London is a city, that has many old buildings and monuments.

Incorrect: London is a city that, has many old buildings and monuments.

Correct: London is a city that has many old buildings and monuments.

No “that” = no comma: A comma should also not be used when that is optional and does not appear.

Correct: The snow that is used to build an igloo must have enough strength to be cut and stacked correctly.

Correct: The snow used to build an igloo must have enough strength to be cut and stacked correctly.

BUT

Incorrect: The snow, used to build an igloo must have enough strength to be cut and stacked correctly.

7. Between two adjectives whose order cannot be reversed

Incorrect: The Caribbean Sea contains some of the world’s most stunning, coral reefs.

(You wouldn’t say, “The Caribbean Sea contains some of the world’s most coral, stunning reefs.”)

Correct: The Caribbean Sea contains some of the world’s most stunning coral reefs.

8. Between adjectives and nouns

Incorrect: The Caribbean Sea contains some of the world’s most stunning coral, reefs.

Correct: The Caribbean Sea contains some of the world’s most stunning coral reefs.

9. Before an open parenthesis

Incorrect: The Caribbean Sea contains some of the world’s most stunning coral reefs, (which are home to thousands of species of marine life), but many of them are in danger because of overfishing and pollution.

Correct: The Caribbean Sea contains some of the world’s most stunning coral reefs (which are home to thousands of species of marine life), but many of them are in danger because of overfishing and pollution.

IV. COLONS

Colons are used to set up lists and explanations.

A colon must always follow a full sentence that makes sense as a complete thought that logically sets up the information that follows. For example, I think is a complete sentence, but it cannot stand by itself. In contrast, I like to think about many things is a statement that logically introduces an explanation of what those things are.

Unlike a semicolon, a colon can be followed by either a full sentence or a fragment.

1. Before a list

Incorrect: On our trip to London, we visited: museums, palaces, and monuments.

Correct: On our trip to London, we visited these tourist attractions: museums, palaces, and monuments.

2. Before an explanation

Correct: When the Manchus took control in China 1644, the Great Wall ceased to have military significance: the empire now extended well north of the wall, and China’s new enemies came from a different direction – across the sea.

In the example above, the second clause explains why the Great Wall ceased to have military significance. Note that in this case, the colon is grammatically identical to a period or semicolon. When any of these punctuation marks is grammatically acceptable, you will not be asked to choose between them.

V. DASHES

1. To indicate non-essential statements within a sentence

Grammatically, dashes are identical to commas when used this way.

Correct: London – which is a very old city – has many new buildings.

2. Before a list, an explanation, or to create a deliberate pause in a sentence

Grammatically, dashes are identical to colons when used this way

Correct: London has many tourist attractions – museums, palaces, and monuments.

Additional Grammar Rules

I. Wordiness/Redundancy

Shorter is better. When multiple answers are grammatically correct and express the same essential information, the shortest one will virtually always be correct. Note that many questions can be answered visually — you can start with the assumption that the shortest answer will be correct, then check it out to be safe.

The construction of the Great Wall of China was an enormous undertaking that occurred

on a very large scale and required over 3,000 workers.

A. NO CHANGE

B. an enormously huge undertaking on a large scale

C. an enormous undertaking, which occurred on a very large scale

D. an enormous undertaking

The correct answer, D, can be determined with near certainty simply by length.

II. Parallel Structure

1. Keep all lists in the same format: noun, noun noun; -ING, -ING, -ING; verb, verb, verb.

Incorrect: Deception expert Pamela Meyer has collaborated with a team of researchers to survey and analyze existing research on lying from academics, law enforcement officers, and working as psychologists.

Correct: Deception expert Pamela Meyer has collaborated with a team of researchers to survey and analyze existing research on lying from academics, law enforcement officers, and psychologists.

2. The same is true when there are only two items joined by “and” or but. Note that when parallel structure involves infinitives (“to + verb”), it is not necessary to repeat the “to” after the first verb.

Incorrect: Deception expert Pamela Meyer has collaborated with a team of researchers to survey and analyzing existing research on lying from academics, law enforcement officers, and psychologists.

Correct: Deception expert Pamela Meyer has collaborated with a team of researchers to survey and analyze existing research on lying from academics, law enforcement officers, and psychologists.

III. Subject-Verb Agreement

Singular verbs end in -s (she walks)

Plural verbs do not end in -s (they walk)

Most common irregular verb = to be. You must know the singular/plural forms of this verb in both the present (is/are) and the past (was/were).

Tip: If you’re not sure where the subject is, look at the beginning of the sentence. If the sentence is long and contains multiple clauses, check the first noun of the clause in which the verb appears.

The most common way that the ACT distracts from subject-verb disagreements is to place a prepositional phrase between the subject and the verb.

Incorrect: Illegal logging in Mexican forests have resulted in the destruction of the monarch butterfly’s habitat.

Correct: Illegal logging in Mexican forests has resulted in the destruction of the monarch butterfly’s habitat.

Also be on the lookout for compound subjects — two singular subjects connected by “and.”

Incorrect: The Monarch and the Red Admiral is among the most common butterfly species in North America.

Correct: The Monarch and the Red Admiral are among the most common butterfly species in North America.

Non-essential clauses can also be placed between subjects and verbs to distract from errors.

Incorrect: The cochineal, a small insect “discovered” by Hernán Cortés in present-day Mexico in 1519, were commonly used as a colorant in painting, sculpture, furniture and textiles from the mid 16th through the mid-19th century.

Correct: The cochineal, a small insect “discovered” by Hernán Cortés in present-day Mexico in 1519, was commonly used as a colorant in painting, sculpture, furniture and textiles from the mid 16th through the mid-19th century.

Other subject-verb agreement errors to know.

Collective nouns (group, country, school, team, board, government, etc.) are singular .

Each, every, and neither are singular .

The number = singular; a number = plural.

Normal word order can be flipped so that the subject comes before the verb, making disagreements difficult to catch (e.g. Beyond the valley lies a house and lake).

IV. Pronoun Agreement

Singular = it, its, itself

Plural = they, them, their, themselves

Singular nouns must take singular pronouns; plural nouns must take plural pronouns. The noun to which a pronoun refers (its antecedent or referent) will not always appear in the same sentence; you may need to look at the sentence before.

Incorrect: Painter Frida Kahlo (1907-1954) was best known for her portraits. It was strongly influenced by indigenous Mexican culture, as revealed by her use of bright colors and dramatic symbolism.

Correct: Painter Frida Kahlo (1907-1954) was best known for her portraits. They were strongly influenced by indigenous Mexican culture, as revealed by her use of bright colors and dramatic symbolism.

V. Verb Tense

1. Tense Consistency

Always keep verb tense consistent with that of other verbs in the paragraph. Paragraphs in the present should stay in the present; paragraphs in the past should stay in the past. Always start by checking the tense of the verbs in the sentence in question, as well as the surrounding sentences (before/after). The underlined verb must match the other verbs.

Incorrect: Painter Frida Kahlo (1907-1954) was best known for her portraits. She is strongly influenced by indigenous Mexican culture, as revealed by her use of bright colors and dramatic symbolism. In her paintings, she combined elements of the classic Mexican tradition with surrealist techniques.

Correct: Painter Frida Kahlo (1907-1954) was best known for her portraits. She was strongly influenced by indigenous Mexican culture, as revealed by her use of bright colors and dramatic symbolism. In her paintings, she combined elements of the classic Mexican tradition with surrealist techniques.

Important: Correct answers to most verb questions are in either the simple past (was, did, ran) or the present. Answers that include more complicated tenses (would have done, will have gone) are virtually always wrong.

2. Present perfect and Past perfect

You should also have some basic familiarity with two additional tenses.

Present perfect – has/have + verb. Describes an action that began in the past and that continues into the present. Signaled by “for” and “since.”

Incorrect: Italy and France are/were tourist attractions for hundreds of years/since the eighteenth century.

Correct: Italy and France have been tourist attractions for hundreds of years/since the eighteenth century.

Past perfect – had + verb. When a sentence describes two completed actions in the past, the past perfect can be used to describe the action that came first.

Most of the time, either the simple past or the past perfect can be used, e.g. “Before Mae Jemison became an astronaut, she studied/had studied science for many years.” When this is the case, you will not be asked to choose between the simple past and past perfect.

When the phrase “by the time” appears, however, the past perfect must be used.

Incorrect: By the time Mae Jemison became an astronaut, she studied science for many years.

Correct: By the time Mae Jemison became an astronaut, she had studied science for many years.

VI. Adjectives & Adverbs (ACT only)

Adjectives modify nouns: the good book, the boring class, the exciting trip

Adverbs modify verbs and usually end in -ly: the girl ran quickly, the top came off suddenly, the wind blew strongly

1. Adjective vs. Adverb

On the ACT, adjectives and adjectives are switched.

Incorrect: The monkey, a traditional Mexican symbol, appears frequent in Frida Kahlo’s paintings.

Correct: The monkey, a traditional Mexican symbol, appears frequently in Frida Kahlo’s paintings.

Remember that adverbs modify adjectives: -LY, no -LY; two -LYs in a row are almost always wrong.

Incorrect: In the Chinese zodiac, people born under the sign of the monkey are thought to be naturally curiously.

Correct: In the Chinese zodiac, people born under the sign of the monkey are though to be naturally curious.

2. Comparatives and Superlatives

Comparative – “adjective + -ER” or “MORE + adjective” (better, stronger, more interesting)

Superlative – “adjective + -EST” or “MOST + adjective” (best, strongest, most interesting)

When -ER is used, MORE should not be used as well.

When -EST is used, MOST should not be used as well.

Incorrect: Mexican folk art exerted a more stronger influence on Frida Kahlo’s paintings than Surrealism did.

Correct: Mexican folk art exerted a stronger influence on Frida Kahlo’s paintings than Surrealism did.

VII. Word Pairs

(N)either…(n)or

Not only…but (also)

As…as

When one of these pairs of words appears in a sentence, the other must appear as well.

Incorrect: Not only did Mae Jemison study science as a girl growing up in Chicago, and she (also) studied ballet.

Correct: Not only did Mae Jemison study science as a girl growing up in Chicago, but she (also) studied ballet.

VIII. Who, Which, and Whom

Note: The ACT, and presumably the new SAT as well, tests “who vs. whom” only in the forms outlined below. You do not need to know anything about direct objects!

1. Who, whom = people, which = things

Incorrect: Frida Kahlo was an artist which gained renown for her portraits

Correct: Frida Kahlo was an artist who gained renown for her portraits

2. “Whom” before a verb = wrong

Incorrect: Frida Kahlo was an artist whom earned renown for her portraits.

Correct: Frida Kahlo was an artist who earned renown for her portraits.

3. “Whom” after a preposition = right

Incorrect: Frida Kahlo is a painter to who many artists owe their inspiration.

Correct: Frida Kahlo is a painter to whom many artists owe their inspiration.

IX. Modification: Dangling and Misplaced Modifiers

Always place modifiers as close as possible to the nouns they modify.

1. When a descriptive phrase begins a sentence but does not contain a subject, the subject must be placed immediately afterward. If the subject is placed elsewhere in the sentence, a dangling modifier is created.

Incorrect: Born in Mexico City in 1907, self-portraits were what Frida Kahlo was best known for. (Who was born in Mexico City in 1907? Frida Kahlo, not “self-portraits.”)

Correct: Born in Mexico City in 1907, Frida Kahlo was best known for her self-portraits.

2. Misplaced modifiers can occur anywhere in a sentence

Incorrect: The Great Wall of China was constructed was by thousands of workers that originally consisted of separated military fortifications. (The sentence makes it sound as if the workers originally consisted of separated military fortifications.)

Correct: The Great Wall of China, originally consisting of separated military fortifications, was constructed by thousands of workers. (This version makes it clear that the Wall originally consisted of separated military fortifications.)

X. Pronoun Case (ACT only)

When pronoun case is tested, it will always be plural: usually proper name + pronoun (Rob and me) or two pronouns (him and me).

If name + pronoun, cross out the proper name and answer by ear.

If two pronouns, cross out each pronoun in turn and answer by ear.

Incorrect: Last year, my mother and me attended the Gathering of Nations, the largest annual meeting of Native Americans in the United States.

Crossed out: Last year, ….me attended the Gathering of Nations, the largest annual meeting of Native Americans in the United States.

Correct: Last year, my mother and I attended the Gathering of Nations, the largest annual meeting of Native Americans in the United States.

Know: the preposition between should always be followed by an object pronoun (me, her, him, them, us).

XI. Idioms and Diction

Incorrect: Could/should/would/might of

Correct: Could/should/would/might have

Than – comparison

Then – sequence of events.

More/less…than, NOT more/less…then

Other diction questions may test prepositions or verbs, but these can only be answered by ear. There is no way to determine the answer by using a rule.

Incorrect: The Great Wall of China might have been more effective with keeping people in than keeping invaders out.

Correct: The Great Wall of China might have been more effective at keeping people in than keeping invaders out.

Incorrect: Some people claim that The Great Wall of China was really built to capture the Emperor’s love of grandiose projects.

Correct: Some people claim that The Great Wall of China was really built to satisfy the Emperor’s love of grandiose projects.

XII. Transitions

Questions testing transitions are more about meaning than grammar. Answers may be grammatically correct but still wrong. Whenever you encounter a transition question, cross out the transition and state the relationship between the sentences/clauses (similar ideas/contrasting ideas) before you look at the answer choices.

Incorrect: The obvious reason for the construction of the Great Wall of China was protection, since China had no powerful enemies at the time construction first began.

The two halves of the sentence express opposing ideas, so a contradictor is needed.

Correct: The obvious reason for the construction of the Great Wall of China was protection, but China had no powerful enemies at the time construction first began.

Important: If there is an OMIT/DELETE option, or an option without a transition, check it FIRST because it will usually be correct (at least on the ACT).

When two transitions have the same meaning (e.g. but/yet) and are both grammatically acceptable in context, both can automatically be eliminated because no question can have more than one right answer.