Synonyms are words, morphemes, or phrases that have the same or nearly the same meaning as another word, morpheme, or phrase in a given language. They are used to improve word choice and avoid overusing the same word. Synonyms can be any part of speech, including nouns, verbs, adjectives, adverbs, and prepositions.

For example, in the English language, the words begin, start, commence, and initiate are all synonyms of one another because they mean the same thing. Similarly, beautiful and attractive are synonyms of each other because they both refer to someone or something that is pleasing to the eye.

It is important to note that words are considered synonymous in only one particular sense. For instance, long and extended in the context of long time or extended time are synonymous, but long cannot be used in the phrase extended family.

Synonyms can also express a nuance of meaning or be used in different registers of speech or writing. Different technical fields may appropriate synonyms for specific technical meanings. Some writers avoid repeating the same word in close proximity and prefer to use synonyms, which is called elegant variation.

Overall, synonyms are an important aspect of language and can help to make communication more precise and effective.