yes

Concise Oxford English Dictionary © 2008 Oxford University Press:
yes/jɛs/

▶exclamation

• 1 used to give an affirmative response.

• 2 responding to someone addressing one or attracting one's attention.

• 3 questioning a remark.

• 4 expressing delight.

▶noun (pl. yeses or yesses) an affirmative answer, decision, or vote.

– origin OE gēse, gīse, prob. from an unrecorded phr. meaning ‘may it be so’.