what is a sow pig

A sow pig is a female pig that has given birth to at least one litter of piglets. Sows are used for breeding and can be distinguished from other female pigs that have not yet given birth, which are called gilts. Sows root in the ground to create depressions and then build nests in which to give birth. The term "sow" is often used interchangeably with "female swine".