Pronouns take the place of nouns. Use them freely rather than the noun unnecessarily. Too often the word such is added to the repeated noun to stress the particular reference:

If confusion may result when pronouns are used with reference to a number of formations, units, etc., or locations of outcrops, avoid beginning sentences with the words there, this, or it:

'Former' and 'latter'

The terms the former and the latter are used instead of a pair of names, nouns, or groups, to avoid repetition. These terms should be used sparingly. They often confuse and irritate the reader, who must look back to be sure of the reference. Short sentences may be clearer if the noun is repeated. If three or more persons or objects are referred to, the words first or last should be used. Latter is frequently and unnecessarily used for another pronoun, as in the following sentence:

Note that had there been only one student, the use of latter's instead of his/her would be necessary to avoid the implication that the party chief was injured.

Pronouns taking singular verbs

There can be a problem deciding if some indefinite pronouns take a singular or a plural verb.

None

Singular when it means 'no one, not one, no person, no thing', but plural when it means 'no persons, no things, not any':

Either, neither, each, and everyone:

The words any and none replace either and neither when the reference is to more than two.

Relative pronouns 'that' and 'which'

These relative pronouns are commonly misused. That should be used when introducing an essential fact, without which the antecedent is incomplete or undefined, as a restrictive adjective clause (a restrictive adjective clause is one that defines, identifies, or restricts the noun that it modifies): The fossils are in the part of the section that Brenda measured; or, The temperatures and pressures of reactions that produce these assemblages can be no more than 2.8 kbar; or, This is the sample that Jack collected. The last sentence could be modified to read: The sample, which Jack collected, was lost in transit; but, in this revised sentence, the emphasis is transferred from Jack to the loss of the sample, and the fact that Jack collected it has become supplementary information (and the clause has, therefore, become nonrestrictive). Note that a restrictive adjective clause has no commas on either side of it.

That in a sentence restricts or defines the meaning of the word or phrase that goes before it:

Which should be used when introducing a new fact about the antecedent as a nonrestrictive adjective clause (a nonrestrictive adjective clause is one that supplies information about the noun that it modifies, but supplementary information, information not essential to the identification of the person, place, or thing to which it refers): The process, which is of recent invention, extracts both the gold and the silver; or, The outcrop, which is on the left bank of the river, consists of sandstone, siltstone, and shale. Note that a nonrestrictive adjective clause is enclosed within commas.

Which neither restricts nor defines, but comments on, or expands, the meaning of the preceding phrase, usually by adding a new thought:

There is some disagreement regarding the use of that and which, but it may be safely said that that introduces the 'restrictive clause' and which introduces the 'nonrestrictive clause'. Note the difference in meaning between the following two sentences:

The choice of that or which sometimes changes the meaning of a sentence. In I am returning the reports, which I have read, the borrower implies that he or she has read them all. If the borrower says I am returning the reports that I have read, it means that the borrower is returning only those reports that he or she has read. Make sure that your choice of that or which conveys the meaning intended.

A test of whether a clause is restrictive or nonrestrictive is to omit it. If its omission changes the meaning, or results in a sentence that does not make sense or is incomplete, it is restrictive.

If it can be omitted without changing the meaning, it is nonrestrictive.

The restrictive clause should not be set off by commas, even if it is decided, for reasons of euphony, clearness, or emphasis, that a which is better than a that to introduce it. A nonrestrictive clause generally is set off by commas, but there are sentences in which, because of context or because of other punctuation, the nonrestrictive clause is not set off by commas.

The omission or inclusion of commas can change the meaning of the sentence, so the writer should bear in mind the importance of commas to accurate communication. For example, consider the difference in meaning between: The hillsides that consist of mudstone and bentonite are unstable (i.e. only specific hillsides), and The hillsides, which consist of mudstone and bentonite, are unstable (i.e. all the hillsides under discussion).

That is used after a superlative:

In current usage that replaces who when the preceding phrase is general in its implication and does not refer specifically to a person or persons:

Phrases such as and which, and who, or and whose require a preceding relative pronoun to justify the and:

The statement applies also when the conjunction but is used.

Where a restrictive clause is followed by an and which clause, both clauses take which:

Relative pronouns 'who' and 'whom'

The purist is as likely to be criticized for insisting on whom in awkward cases as the careless writer who rarely uses it in the proper place. There are exceptions, but none, however, to the following rule. Who is always used as subject, whom as object. In the following two examples the reasoning behind the choice of who or whom is shown in parentheses:

Whom is used after every preposition, because prepositions take the objective case, for example, to whom, from whom. Whom is used after than; (never use than who).

Possessive pronouns

Use the possessive forms my, your, his, her, our, your (pl.), their, whose, when the present participle form of a verb is used as a noun, that is, words ending in -ing: