Select the option which is the most appropriate one word substitution for the given group of words.

A shortened form of a word or phrase

abbreviation

The most appropriate one-word substitution for the given group of words "a shortened form of a word or phrase" is abbreviation.

• Pseudonym is a false name used by an author or artist.
• Precis is a brief summary of a piece of writing.
• Summary is a brief statement of the main points of something.
• Abbreviation is a shortened form of a word or phrase.

The word abbreviation is the most appropriate because it specifically refers to a shortened form of a word or phrase. The other words do not have the same connotation of being a shortened form of something.