Female (symbol: ♀) is the sex of an organism that produces non-mobile ova (egg cells), the type of gamete that fuses with the male gamete during sexual reproduction. Most female mammals, including female humans, have two X chromosomes. Female characteristics vary between different species with some species having pronounced female characteristics, such as the presence of pronounced mammary glands in mammals. There is no single genetic mechanism behind sex differences in different species and the existence of two sexes seems to have evolved multiple times independently in different evolutionary lineages.The word female comes from the Latin femella, the diminutive form of femina, meaning "woman"; it is not etymologically related to the word male. Female can also be used to refer to gender.