Kev nthuav dav yog thaum cov khoom hauv ib qho khoom txav nrawm dua thiab yog li siv qhov chaw ntxiv thaum cov khoom raug cua sov, qhov tshwm sim hu ua expansion. Khoom, kua, thiab gases tag nrho muaj expansion phenomena. Tus nqi nthuav dav ntawm cov kua yog li 10 npaug loj dua li cov khoom khib nyiab, thiab qhov nthuav dav ntawm cov pa roj yog li 100 npaug ntau dua li cov kua.
