【Mood】 , 【humor】 ,  【temper】 ,  【vein】  mean a temporary state or frame of mind in which one emotion or desire or one set of emotions gains the ascendancy.

【Mood】 is the comprehensive term for any such frame of mind, regardless of its particular cause, its particular character, its effect on others, or its length of existence.

【Mood】 carries a stronger implication of pervasiveness and of compelling power than the other terms; also, it may refer not only to the frame of mind, but to its expression in a literary or artistic work or to what is seen or heard in such a way as to evoke a 【mood】 or to harmonize with one’s 【mood】 .

【Humor】  (see also WIT 2 ) applies chiefly to a 【mood】 which is the result of one’s peculiar temperament or of one’s physical or mental condition at the moment; it may be preferable to  【mood】 when the idea of capriciousness or of whimsicality is to be suggested.

【Temper】  (see also DISPOSITION 2 ) applies to a 【mood】 dominated by a single strong emotion, often specifically that of great anger. When qualified by an adjective indicating the controlling emotion,  【temper】 may apply to any 【humor】 that manifests itself in a display of feeling.

【Vein】  (see also TOUCH ) is often used in the sense of  【mood】 but with a stronger implication of transitoriness and seldom with any suggestion of a temperamental or physical basis.