1. Grammar
   1. A grammatical category used in the classification of nouns, pronouns, adjectives, and, in some languages, verbs that may be arbitrary or based on characteristics such as sex or animacy and that determines agreement with or selection of modifiers, referents, or grammatical forms.
   2. One category of such a set.
   3. The classification of a word or grammatical form in such a category.
   4. The distinguishing form or forms used.
   5. The condition of being female or male; sex.
   6. Females or males considered as a group: expressions used by one gender.
2. Sexual identity, especially in relation to society or culture.
3. 1. The condition of being female or male; sex.
   2. Females or males considered as a group: expressions used by one gender.

Usage Note: Traditionally, gender has been used primarily to refer to the grammatical categories of "masculine," "feminine," and "neuter," but in recent years the word has become well established in its use to refer to sex-based categories, as in phrases such as gender gap and the politics of gender. This usage is supported by the practice of many anthropologists, who reserve sex for reference to biological categories, while using gender to refer to social or cultural categories. According to this rule, one would say The effectiveness of the medication appears to depend on the sex (not gender) of the patient, but In peasant societies, gender (not sex) roles are likely to be more clearly defined. This distinction is useful in principle, but it is by no means widely observed, and considerable variation in usage occurs at all levels.