Full stops are used: to mark the end of a sentence:And then you put it in the mail, and you repeat this process ad infinitum until the damn thing sells. to mark the end of a group of words that is not a full sentence, but which is complete in itself:Over and over. Again and again. Relentlessly. after abbreviations that consist of the first part of a word:Sept. Thurs. in email and website addresses:www.oup.com.