atmos ‘vapor’ + sphaira ‘ball, globe’(sphere)

noun usually in singular

1. the envelope of gases surrounding the earth or another planet:

(天体を取り巻く)大気; 〖the ～〗 (地球の)大気(圏)

e.g. part of the sun's energy is absorbed by the earth's atmosphere.

the air in any particular place:

(特定の場所の)空気

e.g. we couldn't breathe in the dusty atmosphere of his apartment.

(abbreviation atm) Physics a unit of pressure equal to mean atmospheric pressure at sea level, 101,325 pascals.

〘物理〙 気圧〘大気圧の単位; ｟略｠ atm〙

2. the pervading tone or mood of a place, situation, or work of art:

〖具体例ではan (...) ～〗 雰囲気, 環境

e.g. the hotel is famous for its friendly, welcoming atmosphere

e.g. this crisis further compounded the prevailing atmosphere of gloom.

a pleasurable and interesting or exciting mood:

(場所･出来事などの持つ良い)ムード, 趣

e.g. a superb restaurant, full of atmosphere.

mid 17th century: from modern Latin atmosphaera, from Greek atmos ‘vapor’ + sphaira ‘ball, globe’.