/ˌæm.əˈtʊr dɪˈtɛktɪv/ – Phrase
Definition: thám tử nghiệp dư.
A more thorough explanation: An amateur detective is an individual who investigates or solves crimes or mysteries as a hobby or personal interest, rather than as a professional law enforcement officer or private investigator.
Example: The amateur detective conducted his own investigation into the missing person case.