aecium

noun

ae·​ci·​um ˈē-shÄ“-É™m How to pronounce aecium (audio)
ˈē-sē-
plural aecia ˈē-shÄ“-É™ How to pronounce aecium (audio)
ˈē-sē-
: the fruiting body of a rust fungus in which the first binucleate spores are usually produced
aecial
ˈē-sh(Ä“-)É™l How to pronounce aecium (audio)
adjective

Word History

Etymology

back-formation from aecidium "a cup-shaped or spheroidal aecium," borrowed from New Latin, irregularly for *oecidium, borrowed from Greek oikídion, diminutive of oîkos "house, abode, room" — more at vicinity, -idium

Note: Word introduced as a substitute for aecidium by the Purdue University plant pathologist J. C. Arthur (1850-1942) in an effort to reform terminology for rust fungi; see "Terminology of the Spore-Structures in the Uredinales," Botanical Gazette, vol. 39 (Mar., 1905), pp. 219-22. Arthur in the same article introduced aecial and aeciospore. The earlier word aecidium was coined as a genus name by the author and botanist John Hill, in A General Natural History, or New and Accurate Descriptions of the Animals, Vegetables, and Minerals, of the Different Parts of the World, vol. II, A History of Plants (London: Printed for Thomas Osborne, 1751). Hill states on p. 64: "We have called this genus, distinguished by its peculiar cells, Æcidium, from the Greek οικιδιον, cellula." Since the 19th century dictionaries and mycological references have assumed on no grounds other than appearance that the word was borrowed from Greek aikía, "maltreatment, outrage, torture." (See, for example, Miguel Ulloa and Richard T. Hanlin, Illustrated Dictionary of Mycology [St. Paul: American Phytopathological Society, 2000], where aikía is incorrectly glossed "wound, lesion.") Hill might have avoided misinterpretation by transliterating the word oecidium, but given the identity of <ae> and <oe> in English pronunciation, the distinction may have seemed trifling.

First Known Use

1905, in the meaning defined above

Time Traveler
The first known use of aecium was in 1905

Rhymes for aecium

See All Rhymes for aecium

Browse Nearby Words

aeciospore
aecium
aecology
See all Nearby Words

Cite this Entry

“Aecium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/aecium. Accessed 27 Mar. 2026.

Copy Citation

More from Merriam-Webster on aecium

See More

Britannica.com: Encyclopedia article about aecium

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

More from Merriam-Webster

Word of the Day

Listen to the pronunciation of dross

See Definitions and Examples »

Popular in Grammar & Usage

See More

Are You Misusing These 10 Common Words?

5 Verbal Slip Ups and Language Mistakes

Is that lie 'bald-faced' or 'bold-faced'?

The Difference Between 'i.e.' and 'e.g.'

Why is '-ed' sometimes pronounced at the end of a word?
See More

Popular in Wordplay

See More

12 Words for Signs of Spring

The Opposite of Déjà Vu

The Words of the Week - Mar. 27

Why do we call it a 'pipe dream'?

Why do we call it a 'flea market'?
See More

Popular

See More

Are You Misusing These 10 Common Words?

12 Words for Signs of Spring

The Opposite of Déjà Vu
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
little boy with a magnifying glass looking at footprints
Quiz: Spot the Misspelled Word! Think you can detect a spelling error from a mile...
See All