Only vs Unless - What's the difference?

only | unless |

As conjunctions the difference between only and unless

is that only is under the condition that; but while unless is except on a specified condition; if not.

As an adjective only

is alone in a category.

As an adverb only

is without others or anything further; exclusively.

As a noun only

is (rare) only child.



Alternative forms

* onely (obsolete)


  • Alone in a category.
  • * {{quote-magazine, date=2013-07-26, author= Nick Miroff
  • , volume=189, issue=7, page=32, magazine=(The Guardian Weekly) , title= Mexico gets a taste for eating insects , passage=The San Juan market is Mexico City's most famous deli of exotic meats, where an adventurous shopper can hunt down hard-to-find critters such as ostrich, wild boar and crocodile. Only the city zoo offers greater species diversity.}}
  • Singularly Superior; the best.
  • * (William Shakespeare)
  • Motley's the only wear.
  • Without sibling; without a sibling of the same gender.
  • * 1949 , and (Ernestine Gilbreth Carey), (Cheaper by the Dozen) , dedication:
  • To DAD ¶ who only reared twelve children ¶ and ¶ To MOTHER ¶ who reared twelve only children
  • (label) Mere.
  • * , I.40:
  • I know some who wittingly have drawne both profit and preferment from cuckoldrie, the only name whereof is so yrksome and bail-ful to so many men.


    * (alone in a category) sole, lone * (singularly superior) peerless, unequaled, nonpareil

    Derived terms

    * if any * if only * one and only * only child * only game in town * only if


  • Without others or anything further; exclusively.
  • * {{quote-magazine, date=2013-06-07, author= Ed Pilkington
  • , volume=188, issue=26, page=6, magazine=(The Guardian Weekly) , title= ‘Killer robots’ should be banned in advance, UN told , passage=In his submission to the UN, [Christof] Heyns points to the experience of drones. Unmanned aerial vehicles were intended initially only for surveillance, and their use for offensive purposes was prohibited, yet once strategists realised their perceived advantages as a means of carrying out targeted killings, all objections were swept out of the way.}}
  • No more than; just.
  • * 1949 , Frank B. Gilbreth, Jr. and Ernestine Gilbreth Carey, (Cheaper by the Dozen) , dedication:
  • To DAD
    who only reared twelve children
    who reared twelve only children
  • * {{quote-book, year=1963, author=(Margery Allingham), title=(The China Governess)
  • , chapter=20 citation , passage=‘No. I only opened the door a foot and put my head in. The street lamps shine into that room. I could see him. He was all right. Sleeping like a great grampus. Poor, poor chap.’}}
  • * {{quote-magazine, date=2013-06-22, volume=407, issue=8841, page=70, magazine=(The Economist)
  • , title= Engineers of a different kind , passage=Private-equity nabobs bristle at being dubbed mere financiers. Piling debt onto companies’ balance-sheets is only a small part of what leveraged buy-outs are about, they insist. Improving the workings of the businesses they take over is just as core to their calling, if not more so. Much of their pleading is public-relations bluster.}}
  • As recently as.
  • * {{quote-magazine, date=2013-08-03, volume=408, issue=8847, magazine=(The Economist)
  • , title= Yesterday’s fuel , passage=The dawn of the oil age was fairly recent. Although the stuff was used to waterproof boats in the Middle East 6,000 years ago, extracting it in earnest began only in 1859 after an oil strike in Pennsylvania. The first barrels of crude fetched $18 (around $450 at today’s prices).}}
  • (obsolete) Above all others; particularly.
  • * Marston
  • his most only elected mistress

    Derived terms

    * if and only if * only if


    (English Conjunctions)
  • Under the condition that; but.
  • However.
  • But for the fact that; except.
  • Statistics



  • (rare) only child
  • * 2013 , Sybil L. Hart, ?Maria Legerstee, Handbook of Jealousy
  • The consistent finding that infants who are onlies do not differ from those who have siblings despite their lesser history of exposure to differential treatment is perplexing.



    Alternative forms

    * unlesse (obsolete)


    (English Conjunctions)
  • Except on a specified condition; if not.
  • I’m leaving unless I get a pay rise (AmE: raise).
  • *
  • * 1839 , Denison Olmsted, A Compendium of Astronomy Page 95
  • Secondly, When a body is once in motion it will continue to move forever, unless something stops it. When a ball is struck on the surface of the earth, the friction of the earth and the resistance of the air soon stop its motion.


    * (except on a condition) if

    Derived terms

    * precisely unless * unlesss * unless and until, until and unless