/ ɪnˌvestɪˈgeɪʃn; NAmE / noun [ C , U ] investigation (into sth)
1.
an official examination of the facts about a situation, crime, etc. :
a criminal / murder / police investigation
The police have completed their investigations into the accident.
She is still under investigation .
2.
a scientific or academic examination of the facts of a subject or problem
SYN enquiry :
an investigation into the spending habits of teenagers
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WORD ORIGIN
late Middle English : from Latin investigatio(n-) , from the verb investigare , from in- into + vestigare track, trace out.