Periods

Use periods at the end of full sentences. Use only one space after a period in any content type. 

Avoid periods in headings, subheadings, titles, tooltips, field descriptions, and menu names. 

Use periods to complete description text in product copy, messages, and notifications. 

Only use them in a bulleted list if the list item is a complete sentence (see: Lists).

Don't use periods within the letters of a degree.

BS, MBA, PhD
B.S., M.B.A., Ph.D.