Grammar

They're / Their / There

They're is a contraction of they and are. Their is the possessive form of the pronoun they. There is used in reference to a particular place.

Your / You're

Your is the possessive form of the pronoun you. You're is a contraction of you and are.

Its / It's

Its is a possessive pronoun indicating that something possesses something else. It's is a contraction meaning "it is."

e.g. / i.e. / cf.

For example / for instance. That is / in other words. Compare.

Who / That

To refer to a person, use who. To refer to an object, use that.

Who / Whom / Who's / Whose

Who refers to the subject of a sentence. Whom either refers to the object of a sentence or the object of a preposition. Who's is a contraction of "who" and either "is" or "has." Whose shows possession.

Less / Fewer

Less is used as an adjective with non-countable nouns; Less can be a noun meaning "something inferior or not as important," or an adverb meaning "in any way different." Fewer is used to describe nouns that can be counted.

Semicolon / Comma

Semicolons used to join two independent clauses, with conjunctive adverbs, or to identify items in a list with other punctuation. Commas used with conjunctions to join sentences, separate items in a list, or indicate a pause after a beginning phrase.

Between / Among

Use between for exactly two items. Use among for three or more items.