The local form of a language that differs from the main is?

The local form of a language that differs from the main is called a dialect.

Here's a breakdown:

* Dialect: A regional or social variety of a language distinguished by pronunciation, grammar, and vocabulary.

* Main: Refers to the standard or "official" form of the language, often used in formal settings like education and government.

For example, American English is a dialect of the English language, differing from British English in pronunciation, spelling, and certain vocabulary.