to carefully examine the facts of a situation, an event, a crime, etc. to find out the truth about it or how it happened

to try to find out information about somebody’s character, activities, etc.

This is not the first time he has been investigated by the police for fraud.

She is being investigated over allegations of illegal business dealings.

They were investigated on suspicion of drug smuggling.

to find out information and facts about a subject or problem by study or research

The study investigates the effects of feeding a high energy diet to cows.

Researchers are investigating how foreign speakers gain fluency.

LEARNit Dictionary