The Editor's Manual
Free learning resource on English grammar, punctuation, usage, and style.
Both “who” and “that” can refer to people. “Who” is preferred in formal usage.
Use masculine and feminine pronouns like “he” and “she” instead of “it” for animals with names or whose sex is known. To refer to a species or an animal whose sex is not known, use “it” instead.
Use “who” for animals with names, animals that are personified or anthropomorphized, or to indicate emotional closeness. Use “which” or “that” to discuss a species or an unknown animal without a name.
Use “each of” with singular verbs to refer to every one of a group separately. “Each of” may be followed by a plural, gender-neutral pronoun. In spoken English, “each of” is sometimes used with plural verbs to refer to an entire group.
When “each” is part of the subject of a sentence, it is used with singular verbs, except when it follows a plural noun. “Each” may be used with a plural pronoun in an indefinite reference.
The article “the” is generally omitted with acronyms of proper nouns but used with initialisms. “The” is used with an abbreviated common noun if it would be used with the full form.
“That” introduces information that is essential to meaning and not enclosed in commas. “Which” introduces additional, optional details enclosed in commas. In British usage, it also introduces essential information.
Both “than I” and “than me” are grammatically correct, since “than” can be used as either a preposition or a conjunction. “Than I” is seen more often in formal usage.
“It’s me” and “This is him/her” are generally acceptable in everyday usage. The strictly correct alternatives, “It is I” and “This is he/she,” are confined to highly formal usage.
“I” is a subject pronoun, while “me” is an object pronoun. In formal styles, use “I” in a compound subject and “me” in a compound object. “Me” is generally preferred in comparisons and after the “be” verb.