Sire is a formal, old-fashioned way to address a king. In medieval times, when speaking to a monarch, people would say “Yes, sire” or “Please, sire” as a mark of deep respect. You might encounter this word when reading historical fiction or fantasy novels set in kingdoms with castles and courts.

While you might call any polite man “sir” today, sire was reserved exclusively for royalty. A knight would address his king as sire, never his fellow knights or even nobles of lower rank.

In animal breeding, particularly with horses and dogs, sire means a male parent. The sire of a prized racehorse is its father, while the female parent is called the dam. Breeders keep careful records of which animals sired which offspring, tracking bloodlines and inherited traits across generations.

As a verb, to sire means to father offspring. A champion stallion might sire dozens of foals during his lifetime. People also use this verb for humans in formal or historical writing: “The king sired three sons and two daughters.”