olemus
ajamõõtur seadme, komponendi või programmina,
kuid mitte käekell, taimer ega stopper

Wiktionary:
1. an instrument that measures or keeps track of time; a non-wearable timepiece
2. (attributive) a common noun relating to an instrument that measures or keeps track of time
A 12-hour clock system; an antique clock sale; Acme is a clock manufacturer.

vt ka
- ajaaudiitori kell
- ajatempliallika kell
- paroolikell
- taktgeneraator