serves is a form of:

Serf



noun
1.
(A farm labor, bound to his master's land and transferred eight it, a slave vassal) ខ្ញុំកញ្ជះគេ, សេវកា
Example: Noblemen used to employ serfs to work for them.
ENGLISH MEANING
noun
1.
A servant or slave employed in husbandry, and in some countries attached to the soil and transferred with it, as formerly in Russia.