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