2. Ideographic synonyms.

--They bear the same idea but not identical in their referential content.

--Ex.: to ascent – to mount – to climb; To happen – to occur – to befall – to chance; Look – appearance – complexion – countenance

3. Dialectical synonyms.

--Ex.: lift – elevator; Autumn – fall 

4. Contextual synonyms.

--Context can emphasize some certain semantic trades & suppress other semantic trades; words with different meaning can become synonyms in a certain context.

--Ex.: tasteless – dull; Active – curious;

--Synonyms can reflect social conventions.

5. Stylistic synonyms.

--Belong to different styles.

Ex.: To die (neutral) - to kick the bucket (colloquial)

The sources of synonyms: borrowings, shift of meaning, dialectical words, compounds, shortenings, conversion, euphemisms, phrasal verbs («to give up» - «to abandon», «to cut down» - «to diminish»)