Other forms: functionalities
Functionality is what a machine or a program can actually do. The search box, the export button, the part that syncs your phone — all functionality.
The word belongs to software and product meetings, where people ship new functionality or strip functionality out to make a thing simpler. It is a mass noun, so you add functionality rather than adding a functionality. It has a plainer sense too, closer to its root: the functionality of a design is how well it works as opposed to how it looks, and a beautiful chair with poor functionality is one you cannot sit in for long.
1nounfunctionalityThe range of things a machine or program can do.
“The update adds search functionality to the app.”
technical in this meaning — an editor’s judgement
2nounwellHow well something works, as opposed to how it looks.
“The kitchen was redesigned for functionality.”
From functional + -ity.
Etymology from Wiktionary, CC BY-SA