This document provides definitions for key gender-related terms used in development work. It defines sex as the biological characteristics that define humans as male or female. Gender is defined as the socially constructed roles, relationships, and attributes ascribed to the two sexes. Other terms defined include gender equality, gender equity, practical gender needs, strategic gender interests, and gender mainstreaming. Gender analysis and how projects can be designed to be gender-neutral, gender-sensitive, or gender-transformative are also summarized.