(Stands for) Figure 4.3 Semantic triangle (see 王铭玉2001:42; Eco 1990:67)
皮尔士三分法 A trichotomy of signs: icon, index, and symbol
Peirce divides signs by three trichotomies (later he discovered ten trichotomies and sixtysix classes of signs). Firstly, in terms of the characteristics of the sign itself, a sign may be a mere quality, an actual existence, or a general law; Secondly, in terms of relation, signs are divided according as the relation of the sign to its object consists in the sign’s having some character in itself, or in some existential relation to that object, or in its relation to an interpretant; Thirdly, according as its Interpretant represents it as a sign of possible or as a sign of fact or a sign of reason.
能指与所指signifier & signified： 能指与所指 ：
Saussure moves further to explain: “ In our terminology a sign is the combination of a concept and a sound pattern. But in current usage the term sign generally refers to the sound pattern alone, e.g. the word form arbor …the ambiguity would be removed if the three notions in question were designated by terms which are related but contrast. We propose to keep the term sign to designate the whole, but to replace concept and sound pattern respectively by signification and signal. The latter terms have the advantage of indicating the distinction which separates each from the other and both from the whole of which they are part.”(1972, 2001:67)
Signification is the sense of the sign which is the thing or idea the sign refers to, while signal is the form, in most cases the written words. The two are respectively called ‘signified’ and ‘signifier’ later by Saussure’s followers, for example Roland Barthes (1999). Signifier may be regarded as the linguistic form of language, and signified the content. The distinction between signifier and signified reveals the two dimensions of language, namely the dimension of expression and the dimension of content.
2) INDEX “An Index is a sign which refers to the Object that it denotes by virtue of being really affected by that Object. ……It does, therefore, involve a sort of Icon ……” (CP vol. 2: 143). If the sign be an Index, it can be considered as a fragment torn away from the object, the relation between the sign and the object is the relation between the whole and a part. An index reminds us of the existence of its object. For example, the contents of a book may be considered as the index of the book itself. Another example is footprint. Footprint on the sands may remind of presence of a man who has walked away from here.
什么是符号学？ 什么是符号学？
符号学的思想是在20世纪初由瑞士语言学家索绪 尔（Saussure）首先提出的，在其《普通语言 学教程》一书中写道：“我们可以设想有一门研 研 究社会中符号生命的科学… 究社会中符号生命的科学 …我将把它叫做符 号学。符号学将表明符号是由什么构成，符号受 什么规律支配。因为这门科学还不存在，谁也说 不出它将会是什么样子，但是它有存在的权利， 它的地位预先已经确定了。”（索绪尔，1985： 38）
三项式关系（ 三项式关系（triadic relation）： ）： A Representamen is the First Correlate of a triadic relation, the Second Correlate being termed its Object, and the possible Third Correlate being termed its Interpretant. In Peirce’s view, triadic relation, which is formed by three correlates, namely the sign as the first correlate, the object as the second correlate and the interpretant as the third correlate, is the essential characteristic of sign.
3) SYMBOL “A Symbol is a sign which refers to the Object that it denotes by virtue of a law, usually an association of general ideas, which operates to cause the symbol to be interpreted as referring to that Object. It is thus itself a general type or law, that it, is a Legisign. ……and thus the Symbol will involve a sort of Index, …” (CP vol. 2:144) For instance, pigeon is the symbol of peace, scales are the symbol of justice. Symbols stand for their objects by social and cultural conventions, for example, the Great Wall symbolizes China, dragon also symbolizes China because they are conventionally considered so.
This triadic relation can be expressed in diagram as below: Interpretant

Sign
Object
Figure 4.2 Triadic relation (see Eco, 1990:67)
The diagram is transformed to illustrate the Theory of Semantic Triangle co-established by Ogden, C. and Richards, I. A. The basic principle of this theory can be exhibited by a triangle: Concept (Thought) (Symbolizes) Symbol(word) (Refers to) Referent (thing)
符号学基本概念简介
什么是符号？ 什么是符号？ What is a sign? As Peirce sees it, A sign, or representamen, is something which stands to somebody for something in some respect or capacity. (CP vol.2: 135) A sign can be verbal or non-verbal.