Synonyms can be nouns, verbs, adverbs or adjectives, but both words must be of the same part of speech. That means, only a noun can be a synonym of another noun, only a verb can be a synonym of another verb, and so on. One can find sets of synonyms in a thesaurus, which is a book listing groups of related words.
Some words are near-synonyms, which have similar but not exactly the same meaning. Examples of proper nouns, such as names of these languages, having synonyms or near-synonyms include:
The word synonym dates back over 500 years, to late Middle English. The word is derived from Latin from the Greek word sunōnumon, neuter form of the adjective sunōnumos, from sun- meaning 'with' + onoma meaning 'name' in the Greek language. The meaning of the word has remained unchanged for all these centuries. There is even a saying, dating to 1892, Once a synonym, always a synonym. The word has been taught to generations of English-language students and is commonly known by the public. Many other languages have a similar word for synonym with the same or similar spelling.