Cov vitamins yog cov organic molecules (los yog cov txheej txheem sib txuas zoo hu ua vitamers) uas yog qhov tseem ceeb rau cov kab mob hauv cov khoom me me rau kev ua haujlwm metabolic. Cov as-ham tseem ceeb tsis tuaj yeem ua rau hauv lub cev kom muaj nuj nqis kom muaj sia nyob, thiab yog li yuav tsum tau txais los ntawm kev noj zaub mov. Piv txwv li, Vitamin C tuaj yeem tsim los ntawm qee hom, tab sis tsis yog los ntawm lwm tus; nws tsis yog suav hais tias yog vitamin nyob rau hauv thawj qhov chaw tab sis yog nyob rau hauv lub thib ob. Feem ntau cov vitamins tsis yog ib qho molecules, tab sis cov pab pawg ntawm cov molecules hu ua vitamers. Piv txwv li, muaj yim vitamers ntawm vitamin E: plaub tocopherols thiab plaub tocotrienols.