1) Consisting of one element 2) Having a single element 3) Having a single part 4) Having but one component 5) Having one component 6) Having only one component 7) Like certain math operations 8) Molecules of only one kind 9) Monadic 10) Single 1) Single 
pertaining to one. unary operators have one operand, unary numbers use base 1 and one symbol.
[adj] - consisting of or involving a single element or component
adjective consisting of or involving a single element or component; `in a unary operation in a mathematical system one element is used to yield a single result`
pertaining to a function whose domain is a given set and whose range is contained in that set.