--- title: "Mens Rea — Elementary Latin Phrase Meaning & Usage" description: "Mens rea is Latin for 'guilty mind,' a phrase used in English law to describe criminal intent. Learn its grammar, roots, and how it shows up in Latin class." canonical: "https://fiveable.me/elementary-latin/key-terms/mens-rea" type: "key-term" subject: "Elementary Latin" unit: "Unit 11" --- # Mens Rea — Elementary Latin Phrase Meaning & Usage ## Definition Mens rea is a Latin phrase meaning 'guilty mind.' It combines the noun 'mens' (mind) with 'rea,' the feminine of 'reus' (guilty/accused), and it survives in English legal terminology to describe the mental intent behind a crime. ## What It Is Mens rea translates literally as "guilty mind." You can break it down using vocabulary you already meet in Elementary Latin: *mens, mentis* is a third-declension feminine noun meaning "mind," and *reus, rea, reum* is an adjective meaning "guilty" or "accused." Because *mens* is feminine, the adjective takes the feminine form *rea*, a nice example of noun-adjective agreement in action. In modern English this phrase lives almost entirely in law, where it names the mental state or intent behind a crime. For a Latin course, the point is not the courtroom detail but recognizing how a two-word Latin phrase keeps working centuries later. Spotting *mens* and *rea*, knowing why the endings match, and translating the phrase word-for-word is exactly the skill you build when you study Latin phrases used in English and Latin roots in legal terminology. ## Why It Matters This term sits in Unit 11, specifically topic 11.6 (Latin phrases used in English) and topic 11.4 (Latin roots in legal terminology). It matters because it shows the payoff of Latin study: vocabulary and grammar you learn for translation also unlock the Latin hiding inside English. Recognizing *mens* and *rea* lets you decode a phrase you'll meet in law, debate, or academic reading. It also reinforces a core grammar goal of the course, seeing adjective-noun agreement (feminine noun, feminine adjective ending) in a real, fixed phrase. ## Connections ### Actus Reus (Unit 11) This is the partner phrase to mens rea. *Actus* means "act" and *reus* means "guilty," so it names the guilty act, while mens rea names the guilty mind. Together they show you the same Latin root *reus* attaching to two different nouns. ### Criminal Intent (Unit 11) Criminal intent is the plain-English idea that mens rea translates. Seeing both side by side helps you connect a Latin phrase to its everyday meaning, which is the whole goal of studying Latin in English. ### Corpus Delicti (Unit 11) Another legal Latin phrase, "body of the offense," that uses the same translation-by-parts strategy. Practicing mens rea trains you to break corpus delicti into *corpus* (body) and *delicti* (of the crime). ### Bona Fide (Unit 11) Like mens rea, bona fide is a fixed Latin phrase where the adjective agrees with its noun (*bona fide*, "in good faith"). Both teach you to notice matching endings inside English borrowings. ## On the AP Exam In Elementary Latin this comes up on vocabulary and translation work, not a courtroom test. Expect to translate the phrase literally ("guilty mind"), identify the root words *mens* and *reus/rea*, and explain why the adjective ends in *-a* to agree with the feminine noun *mens*. On quizzes covering Latin phrases in English, you might match mens rea to its meaning or to its legal-English context, or pair it with actus reus. In short-answer or discussion work, you may be asked how the phrase shows Roman law's lasting influence on English. ## mens rea vs Actus Reus Mens rea means "guilty mind" (the intent), while actus reus means "guilty act" (the action itself). They share the Latin word *reus* ("guilty"), but *mens* is the mind and *actus* is the act. Don't let the shared *reus* make you blur the two. ## Key Takeaways - Mens rea is Latin for "guilty mind," built from *mens* (mind) plus *rea*, the feminine form of *reus* (guilty). - The adjective is *rea*, not *reus*, because it agrees with the feminine noun *mens*, a clear example of noun-adjective agreement. - It survives in English mainly in legal terminology, where it refers to criminal intent. - Its companion phrase is actus reus ("guilty act"); mens rea is the mind, actus reus is the action. - Knowing the parts (*mens*, *reus*) lets you decode the phrase without memorizing it as one chunk. ## FAQs ### What does mens rea mean in Latin? It literally means "guilty mind," from *mens* (mind) and *rea*, the feminine form of the adjective *reus* ("guilty" or "accused"). In English it refers to the criminal intent behind an act. ### Why is it 'rea' and not 'reus' in mens rea? Because the noun *mens* is feminine, the adjective takes the feminine form *rea*. It's the same agreement rule you practice when matching adjectives to nouns in any Latin sentence. ### Is mens rea the same as actus reus? No. Mens rea is the "guilty mind" (the intent), while actus reus is the "guilty act" (the action). They share the word *reus* ("guilty") but pair it with different nouns, *mens* versus *actus*. ### Do I need to know criminal law to study mens rea in Latin? No. For Elementary Latin you mainly need to translate the phrase and identify its root words; the legal background just shows why this Latin phrase still appears in English today. ### How do you break mens rea into its Latin parts? *Mens, mentis* is a third-declension feminine noun meaning "mind," and *reus, rea, reum* is an adjective meaning "guilty." Put together as the feminine *mens rea*, they read "guilty mind." ## Related Study Guides - [11.6 Latin phrases used in English](/elementary-latin/unit-11/latin-phrases-english/study-guide/VwZ0WkG5obe1HrAy) - [11.4 Latin roots in legal terminology](/elementary-latin/unit-11/latin-roots-legal-terminology/study-guide/j9FU9Wb8X0R62i90) ## About This Document Canonical Fiveable pages are available as Markdown at the same path plus `.md`. - [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns - [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing - [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`) - [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/elementary-latin/key-terms/mens-rea#resource","name":"Mens Rea — Elementary Latin Phrase Meaning & Usage","url":"https://fiveable.me/elementary-latin/key-terms/mens-rea","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/elementary-latin/key-terms/mens-rea#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-06-29T17:36:51.980Z","isPartOf":{"@type":"Collection","name":"Elementary Latin Key Terms","url":"https://fiveable.me/elementary-latin/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/elementary-latin/key-terms/mens-rea#term","name":"mens rea","description":"Mens rea is a Latin phrase meaning 'guilty mind.' 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