悪質[akushitsu] bad quality
悪質化[akushitsuka] worsening
異質[ishitsu] different (quality, nature)
音楽の素質[ongakunososhitsu] aptitude for music
音質[onshitsu] tone quality

可塑物質[kasobusshitsu] plastics
画質[gashitsu] image quality (film, video, etc.)
灰白質[kaihakushitsu] gray matter
企業体質[kigyoutaishitsu] financial content
器質的[kishitsuteki] organic