public signs如何用英文定义呢？

你可以参考如下论文：
http://www.12edu.cn/lunwen/yylw/200902/246966.shtml

A sign is an entity which signifies another entity. A natural sign is an entity which bears a causal relation to the signified entity, as thunder is a sign of storm. A conventional sign signifies by agreement, as a full stop signifies the end of a sentence. (Contrast a symbol which stands for another thing, as a flag may be a symbol of a nation)

The way in which a sign signifies is a topic in philosophy of language, see also Meaning (linguistic)

Any given signifier or symbol is dependent upon that which is intended, expressed, or signified in a semiotic relationship of signification, significance, meaning, or import. Thus, for example, people may speak of the significance of events, the signification of characters, the meaning of sentences, or the import of a communication. These diff