電(dian)阻器是(shi)限(xian)制電(dian)流的(de)元件，通常簡稱為電(dian)阻，是(shi)一種最常用的(de)電(dian)子元件，普(pu)遍應用在(zai)各(ge)類(lei)電(dian)子電(dian)路中(zhong)。不但金屬導體有電(dian)阻，其(qi)他物體也有電(dian)阻。

簡單來說(shuo)(shuo)，電(dian)(dian)(dian)(dian)阻(zu)就(jiu)是指電(dian)(dian)(dian)(dian)流(liu)在電(dian)(dian)(dian)(dian)路(lu)中所遇到的(de)阻(zu)力(li)，或者說(shuo)(shuo)是指物體(ti)對電(dian)(dian)(dian)(dian)流(liu)的(de)阻(zu)礙才能。電(dian)(dian)(dian)(dian)阻(zu)越(yue)(yue)大，電(dian)(dian)(dian)(dian)流(liu)所遭(zao)到的(de)阻(zu)力(li)就(jiu)越(yue)(yue)大，因(yin)而電(dian)(dian)(dian)(dian)流(liu)就(jiu)越(yue)(yue)小(xiao)。反之，電(dian)(dian)(dian)(dian)阻(zu)越(yue)(yue)小(xiao)，電(dian)(dian)(dian)(dian)流(liu)所遭(zao)到的(de)阻(zu)力(li)就(jiu)越(yue)(yue)小(xiao)，因(yin)而電(dian)(dian)(dian)(dian)流(liu)就(jiu)越(yue)(yue)大。

電(dian)阻(zu)(zu)的(de)符(fu)號是“R”。電(dian)阻(zu)(zu)的(de)單位為歐(ou)姆(mu)，簡稱(cheng)歐(ou)，用字(zi)母“Ω”表示。常(chang)用的(de)電(dian)阻(zu)(zu)單位還(huan)有千歐(ou)姆(mu)（KΩ），兆(zhao)歐(ou)姆(mu)（MΩ）。