Explanation:

Mail merge consists in combining mail and letters and pre-addressed envelopes or mailing labels for mass mailings from a form letter. Microsoft Word can insert content from a database, spreadsheet, or table into Word documents.
A thesaurus is a reference work that lists words grouped together according to similarity of meaning, in contrast to a dictionary, which provides definitions for words, and generally lists them in alphabetical order.
Spell check is a software program that corrects spelling errors in word processing, email and online discussions. Spell check identifies and corrects misspelled words