有a则是肯定意思“一些”,无a是否定意思“没有、几乎没有”。
few / a few用来修饰可数名词:He has a few friends. 他有几个朋友。He has few friends. 他没几个朋友。而a little、little是用来修饰不可数名词,a little也可以修饰形容词和副词,尤其是比较等级:I can speak only a little Chinese. 我会说一点中文。I know little English. 我几乎不懂英文。We may come a little later. 我们可能会晚点来。