The term keyword in reference to Search Engine Marketing (SEM) usually refers to a word or keyword phrase (combination of words, such as 'Chicago Courier Service') used to find relevant and useful web pages.

It may also mean:

• Keyword (computer programming), an identifier in a computer language that indicates a specific command
• Keyword (linguistics), a word that occurs with unexpected frequency in a text,

or a word which occurs in a text more often than we would expect to occur by chance alone

• Keyword (search) or keyword phrase, a word or phrase to find information in either physical or electronic libraries
• Keyword (Internet search) or keyword phrase, a word or a phrase used to find useful results in internet searches
• Smart keyword, shortcut for bookmarks in Firefox

In a non-computer sense:

• Keywords: A Vocabulary of Culture and Society - a 1976 book discussing English words and their cultural use
• List of Magic: The Gathering keywords