photocell vs sensing element

photocell and sensing element both are nouns.

Word	Noun	Adjective	Verb	Adverb
photocell	Yes	No	No	No
sensing element	Yes	No	No	No

As nouns, sensing element is a hypernym of photocell; that is, sensing element is a word with a broader meaning than photocell:

photocell: a transducer used to detect and measure light and other radiations
sensing element: any device that receives a signal or stimulus (as heat or pressure or light or motion etc.) and responds to it in a distinctive manner

Other hypernyms of photocell include detector, sensor, transducer.

photocell (noun)	sensing element (noun)
a transducer used to detect and measure light and other radiations	any device that receives a signal or stimulus (as heat or pressure or light or motion etc.) and responds to it in a distinctive manner