Sire is a term used to describe a vampire who has created another vampire (referred to as their childe).
A sire is a vampire that has Embraced a childe. The term is unisex, applying to both male and female vampires (thus a female vampire is not a dam, but is also a sire). Alternatively, the term may apply to the act of the Embrace itself, i.e. one may be said to have sired a childe. Similarly, one's sire's sire is one's grandsire, although that particular distinction may not be particularly relevant. Typically, a fledgling's sire is held accountable for the new childe's actions until such a time that the childe is capable of striking out on their own.
Due to the nature of generation, a sire will always be of lower generation than their childe unless said childe lowers their generation via Diablerie.