How to say "altitude" in Japanese

• 高度こうどJLPT N2approx.Common
  nounThe word for altitude as a measured quantity: an aircraft's height in flight, or a point's height above sea level. It has a technical, scientific feel.
  これより次第しだいに高度こうどを下さげてまいります。↗

  We are beginning our descent.
• 高さたかさCommon
  nounReally the everyday word for height — how tall a person, building, or mountain is. It can serve as 'altitude' in loose, general use, but for measured altitude 高度 is the word you want.
  水みずは私のひざの高たかさだった。↗

  The water came up to my knees.

Choose 高度 for altitude as a measured value, as in aviation or heights above sea level; choose 「高さ」 for everyday height, and for 'altitude' only in loose, non-technical talk.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 高度こうどaltitude
• 高さたかさheight
• 高所こうしょhigh place