noun · 9 senses · updated from the 2026-07-25 local source snapshot
Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.
Sound
Pronunciation
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/ˈeɪ.tɹi.əm/
Southern-England:Recorded audio is listed in the source snapshot.
CMU ARPABET:EY1 T R IY0 AH0 M
Digits mark lexical stress: 1 primary, 2 secondary, 0 unstressed.
1
noun
Meaning 1
A central room or space in ancient Roman homes, open to the sky in the middle; a similar space in other buildings.
Definition source: English Wiktionary via Wiktextract
Topics: architecture
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
2
noun
Meaning 2
A square hall lit by daylight from above, into which rooms open at one or more levels.
Definition source: English Wiktionary via Wiktextract
Topics: architecture
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
3
noun
Meaning 3
A cavity, entrance, or passage.
Definition source: English Wiktionary via Wiktextract
Topics: anatomy, medicine, sciences
Examples
an atrium of the infundibula of the lungs
Meaning relationships
Synonyms: none provided
Antonyms: none provided
4
noun
Meaning 4
Any enclosed body cavity or chamber.
Definition source: English Wiktionary via Wiktextract
Topics: biology, natural-sciences
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
5
noun
Meaning 5
An upper chamber of the heart that receives blood from the veins and forces it into a ventricle. In higher vertebrates, the right atrium receives blood from the superior vena cava and inferior vena cava, and the left atrium receives blood from the left and right pulmonary veins.
Definition source: English Wiktionary via Wiktextract
Topics: anatomy, medicine, sciences
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
6
noun
Meaning 6
A microscopic air sac within a pulmonary alveolus.
Definition source: English Wiktionary via Wiktextract
Topics: anatomy, medicine, sciences
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
7
noun
Meaning 7
A cavity inside a porate aperture of a pollen grain formed by the separation of the sexine and nexine layers, widening toward the interior of the grain.
Definition source: English Wiktionary via Wiktextract