Definition of "-s" []

• Used to form plural nouns: letters. (suffix)
• Used to form the third person singular present tense of all regular and most irregular verbs: looks; holds. (suffix)
• Used to form adverbs: They were caught unawares. He works nights. (suffix)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Look at how -s performs multiple roles in Modern English: the English as a Second Language teacher says the word bridge."
• "English-speakers then absorbed the French word for the game, employing English variations of the French plural eschecs, including chesses and chestes and chesse, before settling on chess, which carries the vestigial -s ending inherited from the French."
• "Things might have turned out differently for Modern English if the genitive ending for another class of Old English noun had prevailed over the one taking an -s."