Gender, grammatically, refers to the classification of words by sex into masculine, feminine, and neuter (for objects with no specific sex characteristics). The English language assigns gender only to pronouns (he, she, it) and certain nouns (woman, man).
Specific individual adults should be referred to with masculine or feminine pronouns (he, she, him, her). Avoid using singular masculine or feminine pronouns, however, when gender is not known. Use a plural pronoun or an article instead.
change
Each student should bring his textbook to class every week.
to
Students should bring their textbooks to class every week.
or
Students should bring the textbook to class every week.
When gender is irrelevant in references to animals, babies, or young children, use the neuter pronoun it.
A baby responds with a characteristic whole-body reflex when it is startled.
(See also agreement of pronouns and antecedents and nonsexist language.)