Which is right...

After someone says something, yell "liar".

After someone says something, yell "liar."

After someone says something, yell "liar."

See the part at this site on quotation marks for words.
http://owl.english.purdue.edu/handouts/grammar/g_quote.html

Okay, thanks!

The correct version of the sentence is "After someone says something, yell 'liar'." The word "liar" should be enclosed in single quotation marks.

When referring to a specific word or phrase in a sentence, quotation marks are used. In this case, since you want to indicate that the word "liar" is what should be yelled, you should use quotation marks. However, it's important to note that the specific rules for using quotation marks may differ depending on the style guide or language convention you are following.

To learn more about the usage of quotation marks, you can refer to the website you provided: http://owl.english.purdue.edu/handouts/grammar/g_quote.html. It offers comprehensive information and examples on how to properly use quotation marks in writing.