Coherent

Definition

Coherent is an adjective meaning (1) logical, consistent, and clearly connected; (2) forming a unified or orderly whole; or (3) in physics, describing waves that maintain a constant phase relationship (e.g., laser light). It can also mean (4) able to speak or think clearly and understandably.

Parts of Speech

• Adjective

Pronunciation

American English

• IPA: /koʊˈhɪrənt/
• Respelling: koh-HEER-ənt

British English

• IPA: /kəʊˈhɪərənt/
• Respelling: koh-HEER-ənt

Etymology

Mid-17th century: from Latin cohaerent-, present participle of cohaerēre “stick together, be connected,” from co- “together” + haerēre “to stick, cling.” The spelling with co- later regularized to coherent.

Derivatives

• coherence (noun) — the quality of being logical and consistent; in physics, a measure of phase correlation
• coherency (noun; less common) — same as coherence
• coherently (adverb) — in a logical, connected manner
• cohere (verb) — to stick together; to be logically consistent
• cohesion (noun; related) — the action of forming a united whole, especially of particles
• cohesive (adjective; related) — characterized by or causing cohesion

Synonyms

• logical
• consistent
• orderly
• connected
• lucid
• articulate
• systematic
• integrated

Antonyms

• incoherent
• illogical
• disjointed
• confused
• inconsistent
• chaotic

Usage

Adjective: “She presented a coherent argument backed by data.” / “The brand now has a coherent visual identity across products.” / “Lasers emit highly coherent light.” / “After some rest he was alert and coherent again.”

Related Terms

• Consistency: Agreement among parts of a system or argument; a feature of coherence.
• Structure: Organized arrangement that often produces coherence in writing or design.
• Phase (physics): The relative alignment of wave cycles underlying optical/electromagnetic coherence.
• Signal-to-noise ratio: In communication, higher SNR often improves perceived coherence of speech/data.

Detailed Definitions

Adjective

• Logical and consistent; making sense as a whole — of arguments, explanations, plans, or narratives.
  • Example: “The policy paper is coherent and aligns with prior legislation.”
• Forming a unified or orderly whole — of systems, designs, teams, or strategies whose parts fit together.
  • Example: “The exhibition tells a coherent story from room to room.”
• (Of a person) Able to speak or think clearly — especially after confusion or illness.
  • Example: “The patient became coherent once the medication wore off.”
• (Physics) Having a constant phase relationship — of waves with fixed frequency and phase difference; producing interference patterns.
  • Example: “Interferometers require two coherent light sources.”