The present paper aims to categorize different types of synonymous words and also to highlight their synonymic pattern as well as grammatical categories found in Wordnet of Assamese language. Synonymy is an important component of vocabulary of the language. It establishes lexical relation between words. In fact, the term ‘synonymy’ is applied to the two or more words which share the same semantic features. WorldNet is a lexical database consisting of synsets. A synset is constructed by assembling a set of synonyms that together define a unique sense and synset is the basic foundation of Wordnet. Assamese language is rich in synonyms. In Assamese WorldNet, more than 20,000 synsets are entered under the categories of Noun, Verb, Adverb and Adjective. These synsets can of different types according to their semantic similarity, connotation, denotation, stylistic variations etc.