The number of males in a population per each 100 females.
The proportion of males to females in a population, usually expressed as the number of males per 100 females. The primary sex ratio, at the time of fertilization, is in theory 50% male. The secondary sex ratio, found at birth, usually indicates slightly fewer girls than boys.
The ratio of males to females in a given population, usually expressed as the number of males per 100 females. It is used in defining the proportion of births of the two sexes or in the representation by sexual distribution in certain diseases.