这3个动词均有“哭”之意。
cry : 普通用词。指因痛苦、悲哀或伤感等出声地哭。
The baby can cry as soon as he is born.（婴儿生下来就会哭 。）
weep : 书面用词，指小哭或无声地哭，侧重流泪。
She wept her sad fate.（她为她的悲惨命运而哭泣。）
sob : 指抽泣、呜咽。
The child started to sob when he couldn't find his mother.（孩子因找不到他妈妈哭了起来。）
