A neonate is a recently embraced vampire that has passed through the initial stages of vampiric existence, the fledgling stage. It is the sire's responsibility to ensure that the childe does not embarrass itself or its sire in vampiric society. Derogatorily, a neonate is often called a whelp.
Neonates are generally lightly involved in the true machinations of undead society. They aren't powerful enough to really matter, and are consequently used primarily as pawns by their elders.
After approximately a century of unlife a vampire is called an ancilla.