JOHNSON gets mail. Tom K., a reader in Ottawa, asks:

I had always understood English to be a reasonably easy language to learn, because it lacks many of the features that make other languages difficult. However, a friend told me that English is considered one of the most difficult languages to learn, because it contains so many words that are pronounced the same but have different meanings. I'd love to see your opinion about this (and if I'm right, bragging rights with my friend).

Johnson is sorry to disappoint, but the boring answer is “it depends”. Whether English is confusing or easy mostly depends on the learner’s native language. A native speaker of German or Dutch—Germanic languages closely related to English—will find English relatively straightforward. Learners whose first language is Chinese (completely unrelated) or Russian (distantly related) will find English much harder. This is roughly true of languages all around the world. If you learn a language geographically close and from a common ancestor of your first language, there will be fewer nasty surprises, at every level from sound to word to sentence.

Would it be possible, though, to describe a language's “difficulty” in the abstract? If so, what would it look like? English-speakers often point to a language like Latin or Ancient Greek. Next to them, in one important respect, English is easy. The distinction involves a language's “inflectional morphology”, or the bits and pieces added to a noun or adjective or verb to make it match up with other pieces in a sentence. An English verb has a maximum of five forms (speak, speaks, speaking, spoke, spoken), whereas verbs in Spanish or Latin can take dozens of forms. An English noun usually has only two forms (singular and plural), whereas the Greek or Russian noun takes numerous forms showing grammatical gender, number and case.

This kind of inflection is not a terrible proxy for that slippery idea of "difficulty". Where are the world’s hardest languages, then? Is English one of them? One study, by Gary Lupyan and Rick Dale in 2010, looked closely at inflection. It found that highly inflected languages tend to be spoken by a small number of speakers, and have few neighbours. But languages with big groups of speakers, or many neighbouring languages, systematically tend to have fewer inflections. Why is that? The hypothesis is that as a language spreads over centuries, it is learned by many non-natives (trading partners, conquered subjects and the like). Adults, learning a foreign language imperfectly, avoid using non-necessary endings. And many endings in any language are non-necessary, if other clues (like word order in a sentence) can be recruited to do the same things that word endings do—say, distinguishing the subject of a sentence from its direct object. As languages spread and grow, they are more likely to rely on clues like word order than on word-endings. So “big” languages are “simple”. Under this schema, English fits both criteria: relatively big and relatively simple.

That’s one way of determining relative “hardness”, apart from the starting point of a given speaker’s native language. The problem is that this is far from a perfect measure. Sure, lots of verb-endings are hard for a learner, especially a learner who is not used to them. But where the English verb lacks endings, it makes up for this simplicity in other ways. When to use the various auxiliary verbs is far from obvious: How would you explain to a learner the use of do in the following? “I don’t normally drink, but I do like a crispy lager on a hot summer’s day.” The first use is simply standard with negative statements: we say “I don’t drink” rather than “I drink not.” But the second do, just a few words later, is quite different. It is emphatic, stressing the unusual behaviour on a hot summer’s day. These and other wrinkles can be mind-bending for learners of English.

A recent study by a language-processing company called Idibon tried to establish not which languages are “hard”, but which are “weird”. It used a resource called the World Atlas of Linguistic Structures (WALS). WALS indexes hundreds of languages across hundreds of different features (from whether verbs precede objects to whether the language uses click-sounds as consonants). The Idibon study tried to find which languages use the greatest number of unusual features—ie, those features shared with few other languages. But for tricky methodological reasons, the study had to limit itself 21 features. The languages that have the least “normal” values of these 21 features are the “weirdest”.

Does English rank high? Not especially. Many non-European languages dominate the top of the list. Of those languages in the Indo-European family with English, German, Swedish, Danish, Dutch, Norwegian, Czech, Spanish, Kurdish and Kashmiri all rank as “weirder”. English is at place number 33 of 239 languages in the "weirdness index".

That doesn’t settle a bar bet along the lines of “Is English hard to learn?” But any topic worthy of a good long argument—"Who's the greatest boxer of all time?" "'Dark Side of the Moon' or 'The Wall'?"—should have that element of taste and subjectivity to keep it fun.

Do you have a question or a column idea for Johnson? Write to johnson@economist.com.