A breeder is someone who raises animals carefully and intentionally, selecting which ones to mate so their offspring have desired qualities. Dog breeders, for example, might focus on animals with excellent health, calm temperaments, or specific traits that make them outstanding family pets or skilled working dogs. Horse breeders might work to produce animals with speed, strength, or a gentle nature. Cat breeders carefully select pairs that will produce healthy kittens with the characteristics typical of their breed.

Professional breeders keep detailed records of each animal's ancestry (called a pedigree) and follow strict standards set by organizations dedicated to that species. Responsible breeding requires deep knowledge: breeders must understand genetics, animal health, and proper care. They screen for diseases, provide excellent veterinary care, and ensure their animals live in good conditions.

The word isn't limited to professionals. Someone who raises chickens in their backyard or keeps a few rabbits might also be called a breeder if they're intentionally producing offspring. What distinguishes breeding from simply letting animals reproduce is the careful planning and selection involved, carried out generation after generation to maintain or improve the animals' qualities.