A thesaurus is a tool that can be used to find synonyms, in some cases antonyms, to words you are interested in. It is like a dictionary that helps us find similar words. Thesauruses can come in the book form, or as of more recent, software form. New computer programs just require you to click on a word to find dozens of synonyms in seconds. This is a great tool to have available when you are writing, especially extend assignments where you are writing a great deal of text. It helps avoid using the same word over and over; as this can bore your readers.
In most cases printed versions of thesauri are found arranged in alphabetic dictionary-style arrangements. In most cases, you start by choosing the word you are looking for synonyms for. You will find that word by navigating the alphabetic order of words. Once you locate the word, just look at the synonyms arranged right next to it. Choose another word of interest and just repeat this cycle. This tool has endless applications. It can help you write papers, find new ideas, rewrite a body of work, and even help you write a speech.