Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun investigation

2 senses of investigation

Sense 1
probe, investigation -- (an inquiry into unfamiliar or questionable activities; "there was a congressional probe into the scandal")
       => inquiry, enquiry, research -- (a search for knowledge; "their pottery deserves more research than it has received")

Sense 2
investigation, investigating -- (the work of inquiring into something thoroughly and systematically)
       => work -- (activity directed toward making or doing something; "she checked several points needing further work")