The periods and punctuation

- The period is a full stop, signaling the end of a sentence. This is the most common way to end a sentence (There also exists the exclamation mark (!), and the question mark (?).) While there is some disagreement over how many spaces should go after a period, one space is standard (and two is also acceptable).

It’s cold outside.

- When the sentence ends with quotation marks, the period is placed within the quotation. This is required whether-or-not the quotation includes a period. If either an exclamation point or question mark is used, omit the period completely.

He wouldn’t stop saying the word “literally.” NOT “literally”.
In the speech he asked, “Who will join me?”