Is it possible to buy microsoft Word for my new i mac--I do not want all the office programme?

Not likely, but you can check at www.mactopia.com to see if it's available by itself.

You can try the freeware suite, Libre Office, that is functionally similar to Office 2007 for Windows except it works on Lion.

You may want to consider as well:

These two suites are similar to Libre Office but not as current or as well-supported:

NeoOffice

Open Office

And, then there is Apple's iWork suite:

Pages - word processing and layout

Keynote - presentation

Numbers - spreadsheet

Each can open and save Office compatible files. They may be purchased separately via the Mac App Store for $19.99 each.

(Access to the Mac App Store requires Snow Leopard 10.6.6 or higher and an Apple ID.)

Microsoft Word is not available by itself. However, it is available in the MS Office Mac 2011 Home & Student edition (along with PPT & Excel) for about $100 USD.