Microsoft Word is a word processor developed by Microsoft. It was first released on October 25, 1983 under the name "Multi-Tool Word" for Xenix systems. Subsequent versions were later written for several other platforms including IBM PCs running DOS (1983), Apple Macintosh running Classic Mac OS (1985), AT&T Unix PC (1985), Atari ST (1988), OS/2 (1989), Microsoft Windows (1989), SCO Unix (1994), and macOS (2001). Commercial versions of Word are licensed as a standalone product or as a component of Microsoft Office, Windows RT or the discontinued Microsoft Works suite. Microsoft Word Viewer and Office Online are freeware editions of Word with limited features. 

In 1981, Microsoft hired Charles Simonyi, the primary developer of Bravo, the first GUI word processor, which was developed at Xerox PARC. Simonyi started work on a word processor called "Multi-Tool Word" and soon hired Richard Brodie, a former Xerox intern, who became the primary software engineer. 

Microsoft announced Multi-Tool Word for Xenix and MS-DOS in 1983. Its name was soon simplified to "Microsoft Word". Free demonstration copies of the application were bundled with the November 1983 issue of "PC World", making it the first to be distributed on-disk with a magazine. That year Microsoft demonstrated Word running on Windows.
what platform was it released on in 2001?
macOS