为什么字典上有句子是he fell down from the bike,有的是the tears fell down her face,到底down要加from吗

down 的词性较多：He fell down from the bike.fell down是短语,down 在这做副词The tears fell down her face.这里down 是做介词adv.（坐、倒、躺）下；向下；（表示范围或顺序的限度）下至prep.（从高处）向下；（...