sign for的意思？

The red light is a warning sign for stop.红灯是警告停止行进的信号.Mother winked at Laura as a sign for her to keep silent.母亲向劳拉眨眼示意,叫她不要作声.The postman asked me to sign for the parcel.邮递员叫我签收包裹....

sign for的音标：sign for的英式发音音标为：[sain fɔ:]sign for的美式发音音标为：[saɪn fɔr]...