YALS = Young Adult Literacy Survey (1985)
YALSA = Young Adult Library Services Association, a division of the American Library Association (ALA)
yearlong
year round / year-round
(Hyphenate as adjective preceding its noun; otherwise, open): Her teaching is a year-round commitment. She teaches year round.
young adult (n., adj.)
Young Adult Literacy Survey (1985) = YALS
Young Adult Library Services Association, a division of the American Library Association (ALA) = YALSA
youth (when referring to either an individual or an uncountable collective group; use youths when a number is identified)
YouTube (online video community)
Yu-Gi-Oh!