To Word, the paragraph mark is the end of a paragraph, and the mark stores all formatting associated with a particular paragraph. Each time you press Enter, a paragraph mark is being added. In recent versions of Word, the default is to have some spacing after defined, which means that pressing Enter will create a paragraph with some spacing added. To insert a line break within a paragraph, you can use Shift+Enter (again, at least that's the appropriate key combination in WinWord).

To reset all paragraphs to the default formatting, apply Normal style to all text.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional