Synonyms are words or which have nearly or exactly the same meaning of another word. When the words or phrases have the same meaning then they are known to be the synonyms of each other. Synonyms are generally used in our everyday language. Synonyms are sometimes also called the substitution of the word. For Example-
Synonyms of Hard - Challenging, Difficult, Tough
Similarly, Easy- Simple, Effortless etc.
Big- Start, Commence etc
Appreciate- Cherish, Treasure, Value.