If you learned about grammar in school, you were probably taught to think about "correct" and "incorrect" ways of using a language.

　　Maybe you had to "unlearn" some grammar patterns that you heard at home because your teacher said they were wrong.

　　Prescriptive Grammar

　　The traditional way of teaching grammar in school is called prescriptive grammar. Grammar is seen as a set of rules to follow. The rules are passed from one generation to another. Those who do not follow the rules are looked down upon as being careless or poorly educated.

　　In America, the style of grammar used in academic, government, and professional situations is called Standard American English. There is no official government agency in the United States that makes rules for the English language. In fact, the United States does not even have an official language.

　　Teachers usually rely on tradition and popular style guides to decide what proper grammar is.

　　Descriptive Grammar

　　Descriptive grammar takes a different approach. Descriptive grammarians observe and analyze language as it is used in different communities. They look for rules and patterns that people follow. In descriptive grammar, there is no correct or incorrect way of using grammar.

　　For example, a prescriptive grammarian might say, "Don't use a double negative because it is illogical." A descriptive grammarian might say, "Some communities use double negatives and some do not. Why is that?" We'll talk more about double negatives later.

　　Dr. Richard Epstein is a linguist at Rutgers University in Camden, New Jersey. Dr. Epstein says that most people do not understand the social and political processes behind grammar rules.

　　"Nobody knows why we should not use ‘ain't' or why we should not use double negatives because the teachers teach these things as if they were simply rules that came down from some higher power, authority, maybe God, and there's no rhyme or reason taught for the reason what the reason is for the existence of these rules. So it seems quite boring and totally arbitrary."

　　The Case of the Double Negative

　　Dr. Epstein says grammar rules have nothing to do with logic. Instead, they are based on social fashions, politics, and power. He gives the example of the double negative.

　　As we mentioned on an episode of Everyday Grammar, certain types of double negative words are not allowed in Standard American English. For example, "I don't know nothing." The two words "don't" and nothing" are both negative. Most Americans were taught that double negatives are illogical.

　　In math, two negatives equal a positive. But is this true in language? Does "I don't know nothing" mean "I know something."? Of course not. It just makes a stronger negative. The rule against the double negative does not come from math; it comes from Robert Lowth, the bishop of London.

　　Robert Lowth's book A Short Introduction to English Grammar, first published in 1762, prohibited the double negative. Dr. Epstein says that random grammar rules were a way for the upper classes of London to protect themselves from a rising middle class.

　　"The upper classes became concerned that people below them were getting educated and getting access to sources of power. So to protect their own status and authority people started to prescribe rules for grammar. And if you couldn't follow those rules then you didn't have access to power and authority like the rich people of the day."

　　Ain't ‘ain't' a word?

　　Here's another example. American children are taught that "ain't" is not a word. However, many Americans say "ain't" in place of "is not" or "are not." Listen to this song by Bob Dylan.

　　Someone to open each and every door

　　But it ain't me, babe

　　No, no, no it ain't me, babe

　　It ain't me you're looking for, babe

　　American school teachers told children to stop using the word "ain't" in the 1800s. But long ago, the word "ain't" was the proper negative contraction for "I am not." Ironically, the British upper classes continued to use "ain't" after the Americans banned it. Dr. Epstein explains.

　　"Knowing that regular folks used ‘ain't' but the upper classes of the United States didn't, they created this sort of fake rule that you shouldn't use ‘ain't' because it didn't make sense. Of course it makes perfect sense to anybody who says it. But now we have this rule."

　　So who makes the grammar rules? In America, the grammar patterns of rich white men are the basis of Standard American English, Epstein says. Nobody will go to jail for ignoring grammar rules. But they will have difficulty getting into the best schools and finding good jobs.

　　You ain't seen nothin' yet...

　　B-b-b-baby you just ain't seen nothin' yet

　　I'm Adam Brock.

　　Adam Brock wrote this story for VOA Learning English. Kathleen Struck was the editor.

　　Please leave us a Comment below, and post on 51VOA.COM.