How to Align Only the selected text in word and not all text?

If you are saying that different parts of a text paragraph should have different alignment, use tab stops. For more, see http://wordfaqs.ssbarnhill.com/SettingTabs.htm.

The screen shot below displays a text paragraph where three tab stops have been set: a left-aligned tab stop, a center-aligned tab stop and finally a right-aligned tab stop.

With nonprinting marks displayed, tab characters are represented by arrows pointing to the right.

Alignment is a paragraph property; it cannot be applied to a portion of a paragraph. If changing the alignment for one paragraph is affecting the entire document, then Charles has given you the solution. If (as I suspect), you're wanting to align specific portions of a line, then Stefan has told you how to do that.

If you are using the keyboard shortcuts, and when you apply it to one paragraph, it changes everything, the style applied to that paragraph has the attribute to automatically update from formatting. You need to turn that off!

First, get your style back by undoing or reversing the alignment, so the style has the correct alignment.

Then modify the style and uncheck the box to automatically update.

Slightly more advanced, but even better long term:

In addition to removing the automatically update attribute, consider creating separate paragraph styles for the different justifications you want to use. You can, if you want, attach keyboard shortcuts for those styles. (You could even use Ctrl+E, Ctrl+R, and Ctrl+L to apply those styles.

References:

• The Importance of Styles in Microsoft Word
• Whole Document Reformatted by Suzanne Barnhill, MVP
• Managing Word Styles by Suzanne Barnhill, MVP
• Assigning Keyboard Shortcuts in Microsoft Word 2007-2021 (365)
• Alignment / Justification of Text in Microsoft Word