Noun

• S: (n) operation, functioning, performance (process or manner of functioning or operating) "the power of its engine determines its operation"; "the plane's operation in high winds"; "they compared the cooking performance of each oven"; "the jet's performance conformed to high standards"

Verb

• S: (v) function, work, operate, go, run (perform as expected when applied) "The washing machine won't go unless it's plugged in"; "Does this old car still run well?"; "This old radio doesn't work anymore"
• S: (v) serve, function (serve a purpose, role, or function) "The tree stump serves as a table"; "The female students served as a control group"; "This table would serve very well"; "His freedom served him well"; "The table functions as a desk"
• S: (v) officiate, function (perform duties attached to a particular office or place or function) "His wife officiated as his private secretary"

Adjective

• S: (adj) functioning (performing or able to perform its regular function) "a functioning flashlight"