diaphragm

UK: /ˈdaɪəfræm/ US: /ˈdaɪəˌfræm/ ,(dī′ə fram′)

WordReference Random House Learner's Dictionary of American English © 2025

di•a•phragm /ˈdaɪəˌfræm/   n. [countable]

1. Anatomy a wall of muscle separating two cavities, esp. separating the chest and lungs from the stomach and abdomen:
   When the diaphragm contracts uncontrollably, you get hiccups.
2. Physics a thin disk that vibrates when receiving or producing sound waves, such as in a telephone.
3. Medicine a thin, dome-shaped contraceptive device usually of rubber, that covers the cervix.
4. Optics a device in a camera that controls the amount of light entering the instrument.

WordReference Random House Unabridged Dictionary of American English © 2025

di•a•phragm  (dī′ə fram′), n. 

1. [Anat.]
   • Anatomy a muscular, membranous or ligamentous wall separating two cavities or limiting a cavity.
   • Anatomy the partition separating the thoracic cavity from the abdominal cavity in mammals.
2. Chemistry [Physical Chem.]
   • a porous plate separating two liquids, as in a galvanic cell.
   • a semipermeable membrane.
3. Physics a thin disk that vibrates when receiving or producing sound waves, as in a telephone, microphone, speaker, or the like.
4. Medicine Also called pessary. a thin, dome-shaped device, usually of rubber, for wearing over the uterine cervix during sexual intercourse to prevent conception.
5. Optics a plate with a hole in the center or a ring that is placed on the axis of an optical instrument, as a camera, and that controls the amount of light entering the instrument.
6. Mechanical Engineering a plate or web for stiffening metal-framed constructions.

v.t. 

7. to furnish with a diaphragm.
8. Photography to reduce the aperture of (a lens, camera, etc.) by means of a diaphragm.

• Greek diáphragma the diaphragm, midriff, equivalent. to dia- dia- + phrágma a fence
• Late Latin diaphragma
• Middle English diafragma 1350–1400

Collins Concise English Dictionary © HarperCollins Publishers::

diaphragm / ˈdaɪəˌfræm/ noun

1. any separating membrane, esp the dome-shaped muscular partition that separates the abdominal and thoracic cavities in mammals
2. a circular rubber or plastic contraceptive membrane placed over the mouth of the uterine cervix before copulation to prevent entrance of sperm
3. any thin dividing membrane
4. Also called: stop a disc with a fixed or adjustable aperture to control the amount of light or other radiation entering an optical instrument, such as a camera
5. a thin disc that vibrates when receiving or producing sound waves, used to convert sound signals to electrical signals or vice versa in telephones, etc

Etymology: 17th Century: from Late Latin diaphragma, from Greek, from dia- + phragma fence

diaphragmatic / ˌdaɪəfræɡˈmætɪk/ adjective