A clitic is a word that is grammatically independent, but phonologically dependent, has no stress and is adjacent to another word (words) and is pronounced together with it.

Some forms of clitics:

• shortened verb forms:
  • I'm [aɪm], you'll [ju:l], they've [ðeɪv] and others.
• the article usually merges with the word it defines:
  • an egg [æˈneg], the house [ðəˈhaus]
• the letter s in the formation of the possessive case is a clitic, not an affix, since it can mark not only one noun, but also a nominal group of words or several nouns combined, for example, with the conjunction 'and':
  • the Queen of England's crown
  • Sue and Tom's car