遺憾[ikan] regrettable
憾み[urami] resentment
憾む[uramu] to resent
遺憾に堪えない[ikannitaenai] really regrettable

遺憾なく[ikannaku] amply
遺憾千万[ikansenban] highly regrettable
憾むらくは[uramurakuha] I regret that

化石燃料[kasekinenryou] fossil fuel
可燃[kanen] inflammable
可燃性[kanensei] combustibility
可燃物[kanenbutsu] combustibles
核燃料[kakunenryou] atomic fuel

再燃[sainen] recurrence
代燃車[dainensha] car running on substitute fuel
内燃機関[nainenkikan] internal-combustion engine
燃える[moeru] to burn
燃え移る[moeutsuru] (of fire) to spread

憐れ[aware] pity
憐れみ[awaremi] pity
憐れむ[awaremu] to commiserate
哀憐[airen] pity
可憐[karen] sweet (e.g. young girls, flowers blooming)

同病相憐れむ[doubyouaiawaremu] fellow sufferers pity each other
憐愍[renbin] pity
純情可憐[junjoukaren] pure of heart and beautiful
愛憐[airen] sympathy
憐情[renjou] compassion