YES
YESES
YESHIVA
YESHIVAH
YESHIVAHS
YESHIVAS
YESHIVOT
YESHIVOTH
YESK
YESKED
YESKING
YESKS
YESSED
YESSES
YESSING
YEST
YESTER
YESTERDAY
YESTERDAYS
YESTEREVE
YESTEREVEN
YESTEREVENING
YESTEREVENINGS
YESTEREVENS
YESTEREVES
YESTERMORN
YESTERMORNING
YESTERMORNINGS
YESTERMORNS
YESTERN
YESTERNIGHT
YESTERNIGHTS
YESTERYEAR
YESTERYEARS
YESTREEN
YESTREENS
YESTS
YESTY

38 words start with YES.