beard是可数名词,指“下巴上的胡须”,分单数和复数形式。单数a beard用于描述单个人的胡须整体,如“The artist grew a bushy beard”“He shaved off his beard”;复数beards用于指两个及以上的人各自的胡须,如“all the men... had beards”“sailors... had long beards”。beard无不可数用法,描述胡须时须根据数量用单/复数,如不能说“He has beard”,应说“He has a beard...