Ma'anar ƙamus na kalmar "rarefaction" shine tsari na zama ƙasa mai yawa ko yanayin rashin girma. Yana iya nufin rage matsa lamba ko yawa na iskar gas ko ruwa, ko ga bakin ciki ko raunana wani abu ko abu. A ilimin kimiyyar lissafi, rarefaction kishiyar matsawa ne, kuma galibi ana amfani da shi don bayyana halayen raƙuman ruwa, kamar raƙuman sauti, yayin da suke tafiya ta hanyar matsakaici. A ilmin halitta, rarefaction na iya komawa ga tsarin yin samfura da kwatanta bambancin nau'in halittu a cikin halittu daban-daban.