Definition of onion in English:

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Pronunciation: /ˈənyən/


1An edible bulb with a pungent taste and smell, composed of several concentric layers, used in cooking.
Example sentences
  • In another saucepan cook the garlic and spring onions in the vegetable oil until the onion is soft but not brown.
  • Sweat the onion and diced vegetables in a little olive oil, they should soften and turn golden without browning.
  • To relieve the tension we joked about going home to the smell of grilled onions and peppers.
2The plant that produces the onion, with long rolled or straplike leaves and spherical heads of greenish-white flowers.
  • Allium cepa, family Liliaceae (or Alliaceae).
Example sentences
  • Well I didn't get around to planting the onions last night, but I did dig up the second potato barrel.
  • Bend over the leaves of spring-sown onions just above the neck of each bulb, to help the ripening process.
  • Plant it among the cabbages and with onions and carrots to repel carrot fly.


know one's onions

informal Be very knowledgeable about something.
Example sentences
  • When it comes to real ales and strong continental lagers the landlord really knows his onions, having been lured away from the Fat Cat in Norwich, a pub which wins major awards every single year.
  • There's room here for a few mavericks, including Canadian and Argentine labels, and - should you not know your onions - the young and friendly staff are happy to pass on their own top tips.
  • And you need to know your onions when you tackle Beethoven, even before you get to the details of the music.



Pronunciation: /ˈənyənē/
Example sentences
  • The latter are smoky, but not too smoky; fresh, not crispy; sticky with an oniony, chili-flecked syrup - and flavorful enough that they don't need the ranch.
  • The saucy, oniony beans and yellow rice make it homey.
  • I use them around the garden as companion plants, which means I'm never without the oniony component of salads, soups and stews.


Middle English: from Old French oignon, based on Latin unio(n-), denoting a kind of onion.

  • Onions have been part of the vegetable garden since medieval times, and the name comes ultimately from Latin where it was the word for a large pearl, but used in non-standard speech for an onion. To know your onions is to be very knowledgeable about something. The phrase was first used in the USA in the 1920s, when there were a number of similar phrases that involved knowing a lot about foodstuffs, and onions may simply have been chosen as a widely used vegetable. Another idea is that onions is short for ‘onion rings’, rhyming slang for ‘things’, but this does not fit with an American origin. The same is true of another theory, that there is a link with the lexicographer C. T. Onions, one of the first editors of the Oxford English Dictionary. Despite his eminence as a scholar it seems unlikely that his name would have been widely known on both sides of the Atlantic.

Words that rhyme with onion

bunion, Bunyan, grunion, Runyon

For editors and proofreaders

Syllabification: on·ion

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