The default spacing in Microsoft Word for Mac 2011 is set to120 percent of the default font size. However, you can configure Word for Mac to set single spacing as the default for text in the current ...

Although Microsoft Word adjusts the sentence and word spacing automatically when you paste something, it doesn’t adjust the same for the entire paragraphs. It may create problems when you need to edit ...

I think this would be in your paragraph settings in the Home ribbon. With the Line Spacing widget, go to "Line Spacing Options" and check "Don't add space between paragraphs of the same style".