*Chastity *is the virtue which excludes or moderates the indulgence of the sexual appetite. It is a form of the virtue of temperance, which controls according to right reason the desire for and use of those things which afford the greatest sensual pleasures. According as chastity would exclude all voluntary Carnal pleasures, or allow this gratification only within prescribed limits, it is known as absolute or relative. The former is enjoined upon the unmarried, the latter is incumbent upon those within the marriage state.
You may be confusing this virtue with *continence * (another expression of the virtue of temperance which involves mutually agreed, usually temporary abstinence from even the licit gratifications of marriage).