Translation guide
In Japanese, expressing 'secret investigation' depends on the context: a formal inquiry, undercover work, private sleuthing, or internal corporate probe. The most common and versatile term is 内偵 (naitei), but other words like 秘密捜査 (himitsu sōsa) and 潜入捜査 (sennyū sōsa) are used for specific types of investigations.
To refer to a discreet inquiry or surveillance, often by police or private investigators, without the subject's knowledge.
The most common term for a secret investigation, especially by police or detectives. It implies covert surveillance and information gathering.
The police are conducting a secret investigation on the suspect.
Literally 'secret investigation', used for formal undercover operations, often by law enforcement. More explicit than 内偵.
Through a secret investigation, they uncovered an illegal drug deal.
Undercover investigation where an officer infiltrates an organization. Common in crime dramas.
An undercover agent infiltrated the organization.
Informal term for probing or snooping around, often used in everyday contexts rather than official investigations.
He's secretly probing into the company's internal affairs.
To describe a confidential inquiry within a company, such as into misconduct or compliance issues.
Internal investigation, often confidential. Not necessarily 'secret' but implies a non-public inquiry.
An internal investigation was conducted due to suspicion of misconduct.
Top-secret investigation, emphasizing high confidentiality. Used in corporate or governmental contexts.
To refer to an individual hiring a detective or conducting their own discreet inquiry, e.g., into a spouse's affair.
Background check or personal investigation, often done discreetly. Common in pre-marital checks or suspicion of infidelity.
He requested a secret investigation into his partner's background before marriage.
Investigation into someone's conduct or behavior, often by a private detective. Implies secret surveillance.
To describe secret investigation in the context of spying or national security.
Intelligence activities, espionage. Formal term for secret information gathering by state actors.
The country intensified its secret intelligence activities against neighboring nations.
Spy activities, espionage. More colloquial than 諜報活動.
He was arrested on suspicion of espionage.
内偵 is the broadest term for covert investigation, often surveillance without direct contact. 秘密捜査 is a formal secret investigation, which may include undercover work. 潜入捜査 specifically means infiltration undercover operations.
The direct translation '秘密の調査' is not idiomatic. Use the terms above depending on context.
The top-secret investigation revealed the misconduct.
She hired a detective to secretly investigate her husband's behavior.