IPA: /ˈfʌŋkʃənləs/
KK: /ˈfʌŋkʃənləs/
Not having a specific purpose or role; lacking a function.
The old machine sat in the corner, functionless and forgotten.
Functionless → It is formed from "function" (from Latin "functio", meaning performance or execution) and "-less" (meaning without). The word "functionless" means without function or purpose.
Think of 'function' as performance or execution, and remember that 'functionless' means lacking that performance or purpose.