phon

UK: /fɒn/ US: (fon)

WordReference Random House Unabridged Dictionary of American English © 2026

phon  (fon), n. 

1. Physics a unit for measuring the apparent loudness of a sound, equal in number for a given sound to the intensity in decibels of a sound having a frequency of 1000 cycles per second when, in the judgment of a group of listeners, the two sounds are of equal loudness.

• Greek phōné̄ voice
• 1930–35

phon-, 

1. var. of phono- before a vowel:
   phonic.

phon., 

1. Phonetics phonetics.

Collins Concise English Dictionary © HarperCollins Publishers::

phon / fɒn/ noun

1. a unit of loudness that measures the intensity of a sound by the number of decibels it is above a reference tone having a frequency of 1000 hertz and a root-mean-square sound pressure of 20 × 10^–6 pascal

Etymology: 20th Century: via German from Greek phōnē sound, voice

WordReference Random House Learner's Dictionary of American English © 2026

-phon-, root. 

1. -phon- comes from Greek, where it has the meaning "sound;
   voice.'' This meaning is found in such words as: cacophony, homophone, megaphone, microphone, phonetic, phonics, phonograph, phonology, polyphony, saxophone, stereophonic, symphony, telephone, xylophone.

WordReference Random House Unabridged Dictionary of American English © 2026

pho•no  (fō′nō), n., pl. -nos. [Informal.]

1. Sound Reproduction, Informal Terms phonograph.

• by shortening

phono-, 

1. a combining form meaning "sound,'' "voice,'' used in the formation of compound words:
   phonology.

Also,[esp. before a vowel,] phon-. Cf. -phone, -phony. 

• Greek, combining form representing phōné̄ voice
• 1945–50