By default, Office moves words that do not fit on a line to the next line. If you want, you can use automatic or manual hyphenation to avoid this behaviour:
Automatic hyphenation inserts hyphens where they are needed in a paragraph. This option is only available for paragraph styles and individual paragraphs.
Right-click in a paragraph, and choose Paragraph.
Click the Text Flow tab.
In the Hyphenation area, mark the Automatically check box.
Click OK.
If you want to automatically hyphenate more than one paragraph, use a paragraph style.
For example, enable the automatic hyphenation option for the "Default" paragraph style, and then apply the style to the paragraphs that you want to hyphenate.
Choose View - Styles, and then click the Paragraph Styles icon.
Right-click the paragraph style that you want to hyphenate, and then choose Modify.
Click the Text Flow tab.
In the Hyphenation area, mark the Automatically check box.
Click OK.
Apply the style to the paragraphs that you want to hyphenate.
You can insert a hyphen where you want on a line, or let Office search for the words to hyphenate, and then offer a suggested hyphenation.
To quickly insert a hyphen, click in the word where you want to add the hyphen, and then press Ctrl+Hyphen(-).
If you insert a manual hyphen in a word, the word is only hyphenated at the manual hyphen. No additional automatic hyphenation is applied for this word. A word with a manual hyphen will be hyphenated without regard to the settings on the Text Flow tab page.
Select the text that you want to hyphenate.
Choose Tools - Language - Hyphenation.