noun

• (uncountable) The act of omitting.
• (uncountable) The act of neglecting to perform an action one has an obligation to do.
• (countable) An instance of those acts, or the thing left out thereby; something deleted or left out.
• Something not done or neglected.
• (grammar) The shortening of a word or phrase, using an apostrophe ( ' ) to replace the missing letters, often used to approximate the sound of speech or a specific dialect.