to look into or examine the particulars of (something) carefully so as to discover something hidden, unique, or complex: [no object] The police were called in to investigate. [~ + object] The scientists were investigating the behavior of dolphins.
to look into or examine the particulars of (something) carefully so as to discover something hidden, unique, or complex: [no object] The police were called in to investigate. [~ + object] The scientists were investigating the behavior of dolphins.