How do I keep Word from changing fonts when editing a document?

[TaraKD]

When I'm editing a document, if I delete spaces to move the text from one
paragraph up to join a previous paragraph, Word will often automatically
change the font and/or font size of the text.

Also, sometimes when I cut and paste just simple text within a document (not
switching documents or applications), Word will change the font and/or font
size of the cut text when it pastes it.

 

[Suzanne S. Barnhill]

See http://www.shaunakelly.com/word/styles/FormatOfTextChanges.html