perpetual motion: meaning, definition, pronunciation and examples
C2Formal/Scientific/Technical
Quick answer
What does “perpetual motion” mean?
the hypothetical concept of a machine that, once started, would continue moving forever without requiring additional energy input, violating the laws of thermodynamics.
Audio
Pronunciation
Definition
Meaning and Definition
the hypothetical concept of a machine that, once started, would continue moving forever without requiring additional energy input, violating the laws of thermodynamics.
A state of continuous, uninterrupted movement or activity that seems to sustain itself without external influence; used metaphorically to describe ceaseless energy or constant busyness.
Dialectal Variation
British vs American Usage
Differences
No significant differences in meaning. British usage may occasionally hyphenate ('perpetual-motion') in adjective position more frequently than American.
Connotations
In both varieties, the literal meaning carries connotations of scientific impossibility and theoretical physics. The metaphorical usage suggests tirelessness or unsustainable energy.
Frequency
Equally low-frequency in both varieties, appearing primarily in academic, technical, or metaphorical literary contexts.
Grammar
How to Use “perpetual motion” in a Sentence
be in perpetual motionachieve perpetual motionviolate the laws of perpetual motiondescribe as perpetual motionVocabulary
Collocations
Examples
Examples of “perpetual motion” in a Sentence
verb
British English
- The system cannot perpetuate motion indefinitely.
- They sought to motion perpetually without energy loss.
American English
- No true verb form exists for this compound noun.
adverb
British English
- No standard adverbial form.
American English
- Not applicable.
adjective
British English
- He submitted a perpetual-motion machine design.
- The perpetual-motion concept is fundamentally flawed.
American English
- She wrote about perpetual motion devices.
- It was a perpetual motion proposal.
Usage
Meaning in Context
Business
Metaphorically used to describe a high-energy, constantly productive team or market ('The startup operated like a perpetual motion machine, with deals closing daily').
Academic
Discussed in physics and engineering courses as an example of thermodynamic impossibility; used in philosophy to illustrate theoretical limits.
Everyday
Rare in casual conversation. May appear humorously or hyperbolically to describe a very energetic person ('My toddler is a perpetual motion machine!').
Technical
Precise reference to hypothetical devices violating the first or second law of thermodynamics; subject of numerous patent applications (always rejected).
Vocabulary
Synonyms of “perpetual motion”
Strong
Neutral
Weak
Watch out
Common Mistakes When Using “perpetual motion”
- Using 'perpetual motion' as an adjective without a noun (e.g., 'The system was perpetual motion' – incorrect; should be '...was in perpetual motion' or '...was a perpetual motion device').
- Misspelling as 'perpetual motion' (two words, not hyphenated except in adjective position before a noun: 'a perpetual-motion claim').
FAQ
Frequently Asked Questions
No. According to the first and second laws of thermodynamics, a machine that produces work without energy input or that operates at 100% efficiency is physically impossible.
It is used as a theoretical concept in physics education, as a metaphor for continuous activity, and historically to discuss failed inventions. It also appears in thought experiments.
No, 'perpetual motion' is a compound noun. You cannot say 'to perpetual motion'. Related verbs might be 'to move perpetually' or 'to operate continuously', but these are not standard phrasings of the concept.
'Perpetuum mobile' is the Latin term, often used in musical titles (e.g., a fast-paced piece of music) and in historical scientific texts. 'Perpetual motion' is the English equivalent, more common in modern scientific and general contexts.
the hypothetical concept of a machine that, once started, would continue moving forever without requiring additional energy input, violating the laws of thermodynamics.
Perpetual motion is usually formal/scientific/technical in register.
Perpetual motion: in British English it is pronounced /pəˌpɛtʃuəl ˈməʊʃən/, and in American English it is pronounced /pərˈpɛtʃuəl ˈmoʊʃən/. Tap the audio buttons above to hear it.
Phrases
Idioms & Phrases
- “A perpetual motion machine”
- “Like a perpetual motion device”
- “In perpetual motion”
Learning
Memory Aids
Mnemonic
Think of 'PERPETUAL' as 'forever' and 'MOTION' as 'movement'. A machine that moves forever—though impossible, it's a famous idea.
Conceptual Metaphor
SUSTAINED ACTIVITY IS PERPETUAL MOTION (e.g., 'Her mind was in perpetual motion'). IMPOSSIBILITY IS A PERPETUAL MOTION MACHINE (e.g., 'Getting him to sit still is like building a perpetual motion machine').
Practice
Quiz
In which context is 'perpetual motion' used CORRECTLY?