[ nahyt ]
/ naɪt /




    night and day,
    1. unceasingly; continually: She worked night and day until the job was done.
    2. a complete difference; completely different: The improvement in her grades after tutoring was like night and day.
    Also day and night.

Origin of night

before 900; Middle English; Old English niht, neaht, cognate with German Nacht, Gothic nahts, Latin nox (stem noct-), Greek nýx (stem nykt-)

Related forms

night·less, adjectivenight·less·ly, adverbnight·like, adjective

Can be confused

knight night Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for night and day


/ (naɪt) /


Related forms

Related adjective: nocturnal

Derived Forms

nightless, adjectivenightlike, adjective

Word Origin for night

Old English niht; compare Dutch nacht, Latin nox, Greek nux
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Idioms and Phrases with night and day (1 of 2)

night and day

Also day and night. Continually, without stopping. This phrase is used either literally, as in The alarm is on night and day, or hyperbolically, as in We were working day and night on these drawings. Shakespeare put it by night and day in The Comedy of Errors (4:2): “Time comes stealing on by night and day.”

Idioms and Phrases with night and day (2 of 2)


In addition to the idioms beginning with night

  • night and day
  • night owl

also see:

  • black as night
  • call it a day (night)
  • dead of (night)
  • different as night and day
  • good night
  • make a day (night) of it
  • ships that pass in the night
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.