Abstract: There exists the problem of serious ambiguity in logic concept definitions. This is caused by the fact that in formulating the definition, only one state of the concept of the thing is taken into consideration, neglectful or taking no account of the two absolutely opposite states or the many slightly different states that reflect its objective existence. Therefore, the present article stands for distinguishing the definitions of truth value and non-truth value: in formulating a definition, non-truth-value definition should first be adopted, defining the concept in its general sense; if necessary, truth value definition can then be adopted, distinguishing right from wrong of the concept, so that the definition given will guarrantee in a true and all-round way the various states reflected by the concept.

Key words: logic concept, definition, truth value, non-truth-value