Hom tawv yog txawv, nws tus cwj pwm thiab hluav taws xob kuj txawv txav.
Piv txwv, tawv nyuj yog qhov zoo tshaj plaws uas yog cov khoom haum tsim rau ntau cov khau tawv, tawv tawv thiab cov tawv nqaij cov tawv nqaij; Cov tawv tawv yog lub teeb, nyias thiab muag muag, uas yog cov khaub ncaws zoo nkauj rau cov khaub ncaws; tawv muaj zoo huab cua permeability thiab noo noo permeability.
Nyob rau hauv peb kab ntawm cov khoom, feem ntau cov ntaub ntawv siv yog nyuj tawv thiab yaj tawv.