detection vs spying

detection and spying both are nouns.

Word	Noun	Adjective	Verb	Adverb
detection	Yes	No	No	No
spying	Yes	No	No	No

As nouns, detection and spying are synonyms defined as:

detection and spying: the act of detecting something; catching sight of something

Other synonyms of detection include catching, espial, spotting.

detection (noun)	spying (noun)
the act of detecting something; catching sight of something	the act of keeping a secret watch for intelligence purposes
a police investigation to determine the perpetrator	keeping a secret or furtive watch
the perception that something has occurred or some state exists	the act of detecting something; catching sight of something
the detection that a signal is being received