adj.
Pronunciation: ' ō n-l ē
Function: adjective
Etymology: Middle English, from Old English ā nl ī c, from ā n one ― more at ONE
Date: before 12th century
1 : unquestionably the best : PEERLESS
2 a : alone in a class or category : SOLE <the only one left> <the only known species> b : having no brother or sister <an only child>
3 : FEW <one of the only areas not yet explored>