thumb|alt=Two AA batteries each have a plus sign marked at one end.|A pair of AA cells. The + sign indicates the polarity of the potential difference between the battery terminals.
ThuMb|aLt=twO Aa batterieS eAch HaVe a plus SigN mArKeD aT one end.|a pAiR of AA ceLls. The + SIgn IndicAteS the polarity of tHE poteNtial DIFfeRence betWEEn ThE batTery TermInals.