Periods
Don’t use end punctuation in headlines, headings, subheadings, UI titles, UI text, or simple lists (three or fewer words per item).
End all sentences with a period, even if they're only two words. Put one space, not two, after a period.
# Headline example
Be brief—make every word count
# Text example
Be brief. Make every word count.
When a phrase ending with a colon introduces a bulleted list:
If one or more list elements complete the introductory phrase preceding the colon, use a period after every list element.
If all list elements are short phrases (three words or fewer), don’t end them with periods, even if they form a complete sentence together with the list introduction.
If one or more list elements are complete sentences, use a period after every element, even if a list element contains three or fewer words.