Peace of mind or piece of mind: which is correct?

The short answer

The correct phrase is peace of mind, meaning a state of calm, security, or freedom from worry. Piece of mind is a misspelling that results from mishearing the phrase, since peace and piece are pronounced exactly alike. There is a separate idiom, to give someone a piece of your mind, which means to tell someone angrily what you really think, but that phrase always uses piece, never peace, and the two idioms should never be swapped or confused in careful writing.

Where the confusion comes from

Peace and piece became homophones through separate paths in the history of English, with peace tracing to a Latin word for a truce or calm and piece tracing to an old word for a portion or fragment of something larger.

Because the two words sound completely identical in speech, listeners who only ever hear the phrase peace of mind spoken aloud can easily guess the wrong spelling when they write it down, especially since piece is a far more common word overall in everyday reading.

What each phrase means

Peace of mind describes a settled, worry-free mental state, often achieved through preparation, trust, or resolution of a problem. People say that good insurance offers peace of mind, meaning it reduces anxiety about the future, and a locked door can offer the same reassurance at night.

A piece of mind is not standard English on its own, but the related idiom a piece of your mind means a blunt, often angry opinion delivered directly to someone, as in she gave the driver a piece of her mind after the accident, refusing to hold back her frustration.

Each phrase in a sentence

Locking the doors every night gives her peace of mind while traveling. Knowing the flight was insured brought the family peace of mind. After the neighbor's dog ruined the garden, she marched over to give him a piece of her mind. Regular car maintenance offers drivers peace of mind on long trips, especially before a long cross-country drive.

• Peace of mind: calm, freedom from worry
• A piece of your mind: a blunt, angry opinion

Common mistakes to avoid

Because peace and piece share a pronunciation, writers often type piece of mind when they mean the calm feeling. Not: the warranty gives customers piece of mind; that sentence needs peace, since it describes calm, not an opinion. Only use piece when the idiom involves giving someone your unfiltered opinion, as in a piece of your mind, never when describing a relaxed, worry-free state.

Remember it

Link peace of mind to peaceful, since both words share the same spelling and the same calm meaning. Save piece for the angry idiom, a piece of your mind, where piece means a portion of your opinion being handed over to someone else. If the sentence describes calm or worry-free feelings, spell it peace, and the correct phrase will stay consistent every time you write it.