Gender Disparity: Gender disparity refers to differences between males and females in terms of opportunities, resources, rights, social roles, and power within society.
Gender Gap: A gender gap is a difference between males and females in terms of education attainment levels, income levels, employment opportunities, political representation, etc.
Sex Ratio: Sex ratio is the proportion of males to females within a given population at any given time. It is usually expressed as X number of males per 100 females (or vice versa).