“Mean Girls” is an excellent movie in my book.

And Gretchen Wieners is one smart gal. She understands that you can’t just ask people why they’re white, she knows that cousins and first cousins are the same thing and she will never forget that in girl world, you can only wear jeans or track pants on Fridays.

While she may know the rules of feminism, however, she is definitely not aware of the rules of grammar. We could pass off her mistakes as humor in girl world, but people make these errors on a regular basis in the real world.

We can learn from some of her awful violations of grammar rules.

1. “OK, look, if I was wearing jeans today, I would be sitting over there with the art freaks.”

That may be the case, but Gretchen is not wearing jeans today. Because her idea (of her wearing jeans today) is contrary to fact, she should have used the subjunctive and said, “if I were wearing jeans today …”

2. “Irregardless, ex-boyfriends are just off-limits to friends.”

Sorry, Gretchen: “Irregardless” is not a word. Here is the definition of “regardless,” according to Oxford: “without paying attention to the present situation; despite the prevailing circumstances.” This is usually what people are going for when they say “irregardless.” If “irregardless” were a word, it would mean the exact opposite of what people actually use it for.

3. “Maybe she feels weird around me because I’m the only person that knows about her nose job.”

Here, Gretchen has misused a pronoun. A person is a “who,” not a “that.” Technically, Gretchen’s not exactly incorrect in this case, but she’s not correct either. According to the Purdue OWL, while “that” and “who” can be used when referring to people, “who” is preferred when speaking about a particular person in the formal language.

While the Plastics may not be interested in using formal language, the rest of us really should be.