acorn

noun

ˈā-ˌkȯrn  -kərn 

: the nut of the oak usually seated in or surrounded by a hard woody cupule of indurated bracts

Illustration of acorn

Examples of acorn in a Sentence

Recent Examples on the Web

This expansive set of 50 items comes with artificial pumpkins, artificial leaves, artificial acorns, artificial pine cones and a mesh bag for storage. — Bestreviews, Chicago Tribune, 10 Nov. 2026

Also, consider what deer are eating now, including remaining waste grain, green plots, remaining acorns, but most importantly, woody browse. — Josh Honeycutt, Outdoor Life, 9 Nov. 2026

The study solidifies earlier work from the same team suggesting that acorns and mice affect the number of tick nymphs, says Columbia University disease ecologist Maria Diuk-Wasser, who wasn’t involved in the study. — Clarissa Brincat, Scientific American, 8 Nov. 2026

The Millennium Prize Problems are acorn problems, and Navier-Stokes was one of them. — Rivka Galchen, New Yorker, 1 Nov. 2026

Word History

Etymology

Middle English akorn, akkorn (partially assimilated to corn "kernel, corn entry 1"), hakerne, accherne, accharne, going back to Old English æcern, going back to Germanic *akrana- (whence also Middle High German ackeran "tree nuts," Old Norse akarn, Gothic akran "fruit, produce"); akin to Old Irish írne "sloe, kernel," Welsh eirin "plums, sloes," aeron "fruits, berries," going back to Celtic *agrinyo-, *agranyo-; perhaps further akin to a Balto-Slavic word with an initial long vowel (Old Church Slavic agoda "fruit," Polish jagoda "berry," Lithuanian úoga)

Note: Taken to be a derivative of Indo-European *h₂eǵros "uncultivated field, pasture" (see acre), though this would seem to exclude the Balto-Slavic etymon, which lacks the suffix, from consideration. It is also not clear if fields, uncultivated or not, are the source of wild tree nuts.

First Known Use

before the 12th century, in the meaning defined above

Phrases Containing acorn

• acorn squash
• acorn woodpecker
• acorn worm

Kids Definition

acorn

noun

ˈā-ˌkȯrn  -kərn 

: the roundish one-seeded thin-shelled nut of an oak tree usually having a woody cap