olemus
Merriam-Webster:
: the quality or state of being functional
//a design that is admired both for its beauty and for its functionality

ISO 11863, 15686, 15928, 21929, ISO/IWA 9, ISO/TR 21932 jt:
sobivus või kasulikkus konkreetseks otstarbeks või tegevuseks
=
suitability or usefulness for a specific purpose or activity

ülevaateid
https://www.streetdirectory.com/travel_guide/114346/programming/design_vs_functionality.html

https://www.tdgmarketing.com/insights/aesthetic-design-vs-functionality/

https://www.interaction-design.org/literature/topics/functionality

https://uxdesign.cc/functionality-first-features-second-2d69113cb57b