definition

UK: /ˌdɛfɪˈnɪʃ^ən/ US: /ˌdɛfəˈnɪʃən/ ,(def′ə nish′ən)

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

def•i•ni•tion /ˌdɛfəˈnɪʃən/   n. 

1. the formal statement of the meaning of something:
   [countable] She wrote definitions for "quark'' and "atom.''
2. the condition of being definite:
   [uncountable] The photograph has fine definition.
3. Optics sharpness of the image formed by an optical system:
   [uncountable] Adjust the definition on the TV monitor.

See -fin-.

WordReference Random House Unabridged Dictionary of American English © 2026

def•i•ni•tion  (def′ə nish′ən), n. 

1. the act of defining or making definite, distinct, or clear.
2. the formal statement of the meaning or significance of a word, phrase, etc.
3. the condition of being definite, distinct, or clearly outlined.
4. Optics sharpness of the image formed by an optical system.
5. Radio and Television the accuracy of sound or picture reproduction.

• Latin dēfīnītiōn- (stem of dēfīnītiō), equivalent. to dēfīnīt(us) (see definite) + -iōn- -ion
• Old French diffinition
• Middle English diffinicioun 1350–1400

def′i•ni′tion•al, adj. 
def′i•ni′tion•al•ly, adv. 

Collins Concise English Dictionary © HarperCollins Publishers::

definition / ˌdɛfɪˈnɪʃən/ noun

1. a formal and concise statement of the meaning of a word, phrase, etc
2. the act of defining a word, phrase, etc
3. specification of the essential properties of something, or of the criteria which uniquely identify it
4. the act of making clear or definite
5. the state or condition of being clearly defined or definite
6. a measure of the clarity of an optical, photographic, or television image as characterized by its sharpness and contrast