Origin: Latin suffix -tion
Investigation has 3 different meanings across 1 category:
an inquiry into unfamiliar or questionable activities
"there was a congressional probe into the scandal"
the work of inquiring into something thoroughly and systematically
"The police launched a thorough investigation after discovering discrepancies in the company's financial records."
The act of investigating; the process of inquiring into or following up; research, especially patient or thorough inquiry or examination
"The police launched a meticulous investigation to uncover how the safe was opened without forcing it."
In plain English: An investigation is a careful search for information to figure out what happened.
"The police launched a full investigation after finding the stolen money in the bank vault."
Usage: Use "investigation" to describe a formal process of gathering information to discover facts or solve a problem, such as a police inquiry or a scientific study. It refers specifically to the act of looking into something thoroughly rather than the general idea of researching casually.
The word investigation entered English through the path of Middle and Old French before arriving from its Latin root investigatio. Originally meaning a thorough search or inquiry, it has retained this core sense in modern usage.