It is common to refer biological sex and gender as same thing in the grammatical norms of society. In reality the two words imply different things. Sex is what society assigns a person at birth based on their genitals, whereas gender is a social construct, something that a person learns based on their own internal understanding about where they are on the spectrum of masculinity and femininity. Although the context of terminologies matter, it is important to understand the concepts of difference between sex and gender.
Assigned sex defines the biological and physiological characteristics of a person. the sex of a person is typically assigned based on hormones, chromosomes and genitals.
Although most cultures assume gender based on this assigned sex, Gender refers to the socially constructed roles such as behavior, attributes, and activities that a society or culture considers appropriate for assigned biological sex. Gender is also sometimes referred to as an individual’s own sense of identity. Masculine and feminine are gender categories.
Newborn babies are often assigned a biological sex, male or female, based on their biological organs. Some countries also use a third term, intersex, to define a person’s sex. An individual’s gender is then presumed based on this assigned sex. These preassigned males, females or intersex individuals are expected to take on their gender roles in society based on their presumed gender. For example, if you are assigned male, you are expected to be masculine in appearances and character traits. This classification of sex and gender into two distinct groups, male or female, is called Gender binarism. Most of the cultures follow the gender binary system that predefines gender roles based on male or female classification.
It is easy to understand this distinction between sex and gender if we consider gender as a spectrum of gender identity. A person can be masculine, feminine or somewhere in between. The gender of an individual may differ from assigned sex, for example, a biological woman can be masculine or a biological man can identify as feminine. All individuals have some percentage of both feminine and masculine traits.