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

開け閉て[aketate] opening and shutting
開閉[kaihei] opening and shutting
基地閉鎖[kichiheisa] (military) base closing
自閉症[jiheishou] autism
腸閉塞[chouheisoku] intestinal obstruction

閉まる[shimaru] to be shut
店閉まい[misejimai] closing up shop
閉ざす[tozasu] to shut
閉じる[tojiru] to close (e.g. book, eyes, meeting, etc.)
閉込める[tojikomeru] to lock up