Under it we understand the absence of one-to-one relationship between meaning and form. One form can express several meanings, one meaning can be expressed by several forms. This asymmetry of the relations between form and meaning manifests itself in synonymy, polysemy, homonymy, syncretism, ambiguity, different semantic complications on the syntagmatic level.
Polysemy: to speculate - 1. to think over the idea without having reliable facts; 2. to sell smth hoping to receive more.
Homonymy: 1.Catholic - referring to Catholic church; learned, knowledgeable.
Ambiguity: He left the car with the girl ( We can put several questions to the element underlined: Whom did he leave the car with? What car did he leave? How did he leave the car?).
Syncretism means combining two or more functions or meanings in one form. It was raining and foggy again (was combines the properties of the past continuous auxiliary and of the link verb).
Semantic complications arise syntagmatically, in discourse. Affected by the context, grammatical forms develop newer, connotational meanings ( of emotiveness, expressiveness, intensiveness, positive or negative evaluation):He disliked the girls. He disliked the enthusiasms of American girls (The former plural is customary. The latter plural indicates the character’s ironic (negative) attitude to the girls].