Gender fluidity refers to a gender expression or gender identity that is fluctuating (i.e., changes over time). The term gender fluid can be used as an adjective that describes expression in the context of a different gender identity (“I am a gender-fluid man”) or as a standalone identity term (“I am gender fluid”). To understand gender fluidity, it is important to think about how it relates to expression and identity, as well as the relationship between gender mutability and legitimacy. Critical to ascertaining the meanings behind a fluctuating gender identity and expression is understanding institutional barriers that give meaning to this iteration of gender difference. The following sections discuss the nature of gender fluidity as experienced within a sociocultural context of gender binarism.