plaintiff

noun

plain·​tiff ˈplān-təf 

: a person who brings a legal action compare defendant

Did you know?

We won't complain about the origins of plaintiff, although complain and plaintiff are distantly related; both can be traced back to plangere, a Latin word meaning "to strike, beat one's breast, or lament." Plaintiff comes most immediately from Middle English plaintif, itself an Anglo-French borrowing tracing back to plaint, meaning "lamentation." (The English word plaintive is also related.) Logically enough, plaintiff applies to the one who does the complaining in a legal case.

Synonyms of plaintiff

• complainant
• accuser
• appellant

Examples of plaintiff in a Sentence

the judge ruled that the plaintiff's lawsuit was groundless, and he dismissed it

Recent Examples on the Web

The Los Angeles case was filed by a single plaintiff against Meta, YouTube, TikTok and Snap. —Arkansas Online, 26 Mar. 2026

Today’s top stories A Los Angeles jury found Instagram and YouTube liable for designing their platforms to addict young users, awarding $3 million in damages to a 20-year-old plaintiff. —James Rainey, Los Angeles Times, 26 Mar. 2026

And a cohort of American consumers, siding with the plaintiff, determined that the platforms are defective products, distributed to the public without proper safeguards or warnings about their potential harms. —Maggie Harrison Dupré, Futurism, 26 Mar. 2026

The plaintiffs argue that sportsbook apps—especially when offering live, rapid and in-play wagering options known as microbetting—cause addictions that in turn lead to financial, family and career harms. —Michael McCann, Sportico.com, 26 Mar. 2026

Word History

Etymology

Middle English plaintif, from Anglo-French, from pleintif, adjective

First Known Use

14th century, in the meaning defined above

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Kids Definition

plaintiff

noun

plain·​tiff ˈplānt-əf 

: the complaining party in a lawsuit

Legal Definition

plaintiff

noun

plain·​tiff ˈplān-təf 

: the party who institutes a legal action or claim (as a counterclaim) see also complainant, complaint, libellant compare defendant, prosecution

Etymology

Middle French plaintif, from plaintif, adj., grieving, from plaint lamentation, from Latin planctus, from plangere to strike, beat one's breast, lament