1. Sign and expression
A sign is a thing related with another one. For example, smoke is a sign of fire; the word pencil is a sign of a writing tool.
There are two types of signs: the natural and the artificial or conventional ones. Smoke is a natural sign of fire. That is understood by all the people at all times. When smoke ascends everyone knows that there is a fire down.
The words of a language are artificial or conventional signs. In this case not all peoples understand artificial or conventional signs. For example, the word “house” has a different expression and writing in Spanish, in German or in Chinese.
Expression is a way of saying what someone is feeling, thinking o willing. Through expression we show our mood, affections and desires by means of attitudes, gestures, motions, etc.
We express and communicate our thoughts with words.
We reveal the expression with shouts and gestures and that is common for all men of all races, even among animals. For example: the desire of eating can be expressed by gestures of hands and mouth; the desire of sleeping can be expressed resting your head on your hands.
But expression through language is exclusive to men and every race or ethnic group has a different language. We express our ideas by means of words.