Noun investigation has 2 senses
  1. probe, investigation - an inquiry into unfamiliar or questionable activities; "there was a congressional probe into the scandal"
    --1 is a kind of inquiry, enquiry, research
    Derived form: verb investigate2
  2. investigation, investigating - the work of inquiring into something thoroughly and systematically
    --2 is a kind of work
    --2 has particulars:
     analysis; count, counting, numeration, enumeration, reckoning, tally; police work, police investigation; empiricism; examination, scrutiny; examination, testing; inquiry, enquiry; research; search; tabulation; wiretap, tap
    Derived forms: verb investigate2, verb investigate1