only

Etymology

From Middle English oonly, onli, onlych, onelich, anely, from Old English ānlīċ, ǣnlīċ (“like; similar; equal”), from Proto-Germanic *ainalīkaz, equivalent to one + -ly. Cognate with obsolete Dutch eenlijk, German ähnlich (“similar”), Old Norse álíkr, Swedish enlig (“unified”). Regarding the different phonological development of only and one, see the note in one.

adj

1. Alone in a category.
   He is the only doctor for miles.
   The only people in the stadium were the fans: no players, coaches, or officials.
   He was the only male in attendance at the boyband concert.
   That was the only time I went to Turkey.
   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. 2013-07-26, Nick Miroff, “Mexico gets a taste for eating insects[…]”, in The Guardian Weekly, volume 189, number 7, page 32
2. Singularly superior; the best.
   Motley's the only wear. 1623, William Shakespeare, As You Like It
   The baron had taken a great liking to the Americans and to their ways of doing things, and frequently asserted that America was the only place to live. 1888, United States. Department of State, Papers Relating to the Foreign Relations of the United States, page 316
   "People say there's other games," Jack had said to Cassie at Small Falls earlier that day. "But baseball's the only game." 2015, Mike Lupica, The Only Game, pages 58–59
3. Without sibling; without a sibling of the same gender.
   He is their only son, in fact, an only child.
   To DAD ¶ who only reared twelve children ¶ and ¶ To MOTHER ¶ who reared twelve only children 1949, Frank B. Gilbreth, Jr. and Ernestine Gilbreth Carey, Cheaper by the Dozen, dedication
4. (obsolete) Mere.

adv

1. Without others or anything further; exclusively.
   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. 2013-06-07, Ed Pilkington, “‘Killer robots’ should be banned in advance, UN told”, in The Guardian Weekly, volume 188, number 26, page 6
   My heart is hers, and hers only.
   The cat sat only on the mat. It kept off the sofa.
2. No more than; just.
   To DAD who only reared twelve children and To MOTHER who reared twelve only children 1949, Frank B. Gilbreth, Jr. and Ernestine Gilbreth Carey, Cheaper by the Dozen, dedication
   ‘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.’ 1963, Margery Allingham, chapter 20, in The China Governess
   […] oot of a' six suspects there's not one that's been proved to ha' been nigh the place where the corpse was found, only Mr Graham. 1931, Dorothy L Sayers, chapter 24, in The Five Red Herrings
   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. 2013-06-22, “Engineers of a different kind”, in The Economist, volume 407, number 8841, page 70
   The cat only sat on the mat. It didn't scratch it.
   If there were only one more ticket!
3. As recently as.
   c. 1924-1955, anonymous, The Urantia Book Only yesterday did I feed you with bread for your bodies; today I offer you the bread of life for your hungry souls.
   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). 2013-08-03, “Yesterday’s fuel”, in The Economist, volume 408, number 8847
   He left only moments ago.
4. (Britain) Used to express surprise or consternation at an action.
   She's only gone and run off with the milkman!
5. Introduces a disappointing or surprising outcome that renders futile something previously mentioned.
   They rallied from a three-goal deficit only to lose in the final two minutes of play.
   I helped him out only for him to betray me.
   He met Luis Suarez's cross at the far post, only for Chelsea keeper Petr Cech to show brilliant reflexes to deflect his header on to the bar. Carroll turned away to lead Liverpool's insistent protests that the ball had crossed the line but referee Phil Dowd and assistant referee Andrew Garratt waved play on, with even a succession of replays proving inconclusive. May 5, 2012, Phil McNulty, “Chelsea 2-1 Liverpool”, in BBC Sport
6. (obsolete) Above all others; particularly.

conj

1. (informal) Under the condition that; but.
   You're welcome to borrow my bicycle, only please take care of it.
2. But; except.
   I would enjoy running, only I have this broken leg.
   She would get good results only she gets nervous.
   […] and pleasant it was, only for the dust. April 22 1664, The Diary of Samuel Pepys

noun

1. An only child.
   Sometimes, secondborns marry onlys and the conflicts are similar. 1995, Don Martin, Maggie Martin, Pat Jeffers, Is Your Family Making You Fat?, page 101
   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. 2013, Sybil L. Hart, Maria Legerstee, Handbook of Jealousy
   And in 2016, researchers in China took MRI brain scans and found that, compared with kids with siblings, onlies showed greater flexibility—a measurement of creativity—but lower agreeableness. 2022-11-01, Chiara Dello Joio, “Why Are People Weird About Only Children?”, in The Atlantic