大気圧(たいきあつ)

大気圧(たいきあつ) is the technical term for atmospheric pressure — the pressure exerted by the weight of the air column above a given point.

FORMATION:

• 大気(たいき) ("atmosphere") + 圧(あつ) (from 圧力(あつりょく) "pressure") → 大気圧(たいきあつ)

KEY FACTS (typical contexts):

• The standard reference value is approximately 1013.25 hPa (ヘクトパスカル) at sea level.
• 大気圧(たいきあつ) decreases with altitude — a key concept in mountaineering, aviation, and meteorology.
• The term shows up in physics (気体(きたい)の法則(ほうそく) "gas laws"), engineering (vacuum systems), cooking (high-altitude cooking), and weather forecasting.

COMMON COLLOCATIONS:

• 大気圧(たいきあつ)が下(さ)がる / 上(あ)がる: atmospheric pressure falls / rises
• 標準(ひょうじゅん)大気圧(たいきあつ): standard atmospheric pressure
• 大気圧(たいきあつ)の変化(へんか): changes in atmospheric pressure
• 大気圧(たいきあつ)下(か)で: under atmospheric pressure (in scientific writing)

SIMILAR / RELATED TERMS:

• 気圧(きあつ): atmospheric pressure (everyday and meteorological term) — the word used in daily weather reports and forecasts. Largely interchangeable with 大気圧(たいきあつ) in casual contexts. 気圧}{配置(はいち) "pressure pattern," 高(こう)気圧(きあつ) "high-pressure system," 低(てい)気圧(きあつ) "low-pressure system" all use the shorter form.
• 高(こう)気圧(きあつ): high-pressure system
• 低(てい)気圧(きあつ): low-pressure system
• 気圧計(きあつけい): barometer (instrument for measuring air pressure)
• 気圧(きあつ)配置(はいち): atmospheric pressure pattern (a forecasting term)
• ヘクトパスカル: hectopascal (hPa) — the standard unit used in Japanese weather reports

USAGE NOTES:

• In everyday weather conversation, native speakers usually say 気圧(きあつ), not 大気圧(たいきあつ) (e.g., "今日(きょう)は気圧(きあつ)が低(ひく)いから頭(あたま)が痛(いた)い" "the air pressure is low today, so my head hurts").
• 大気圧(たいきあつ) is preferred in textbooks, academic writing, and contexts where the contrast with vacuum or other reference pressures matters (e.g., "大気圧(たいきあつ)下(か)で" "under atmospheric pressure" in chemistry experiments).