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

隠密[onmitsu] privacy
過密[kamitsu] overcrowding
確率密度関数[kakuritsumitsudokansuu] probability density function
機密[kimitsu] secrecy
機密性[kimitsusei] confidentiality

機密保護[kimitsuhogo] security (e.g. data, password, etc.)
気密[kimitsu] airtight
気密室[kimitsushitsu] airtight chamber
緊密[kinmitsu] rigour
軍事秘密[gunjihimitsu] military secret