Having one component

• Of one kind, in chemistry
• Having only one component
• Consisting of a single element
• Like certain math operations
• Acting on a single number, mathematically
• Consisting of a single element or component

Wiktionary Word definitions in Wiktionary
a. 1 Consisting of or involving a single element or component. 2 (context mathematics programming computer engineering English) Of an operation, function, procedure(,) or logic gate, taking exactly one operand, argument, parameter(,) or input; having domain ...

WordNet Word definitions in WordNet
adj. 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"

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
1923, from Latin unus "one" (see one ) on model of binary , etc.