A thesaurus is most helpful for students who must find the correct pronunciation for a difficult new word.
need to find multiple definitions for one word.
would like to keep their writing from becoming repetitive.
are looking for multiple forms of one word.

Excerpt from jane eyre charlotte bronte 2 i was glad of it: i never liked long walks, especially on chilly afternoons: dreadful to me was the coming home in the raw twilight, with nipped fingers and toes, and a heart saddened by the chidings of bessie, the nurse, and humbled by the consciousness of my physical inferiority to eliza, john, and georgiana reed.