私立探偵[shiritsutantei] private detective
探偵[tantei] detective
探偵小説[tanteishousetsu] detective story
偵察[teisatsu] scout out
偵察衛星[teisatsueisei] reconnaissance satellite

偵察機[teisatsuki] reconnaissance plane
偵察隊[teisatsutai] scouting party
偵知[teichi] spying
内偵[naitei] secret investigation
密偵[mittei] spy