How to say "triangle" in Japanese

• 三角さんかくJLPT N2approx.Common
  nounThe general word for a triangle or triangular shape. Use it when you simply mean something triangle-shaped, such as a sign or a piece of food, rather than the figure as a mathematical object.
• トライアングルCommon
  nounRefers only to the musical instrument, the metal percussion instrument struck with a beater. It is not a way to refer to the geometric shape, so it is the word you want only in musical contexts.
• 三角形さんかくけいCommon
  no-adjectiveNames the geometric figure itself, a three-sided shape. It suits mathematical or descriptive contexts where you are talking about the shape as such, and overlaps with 三角 in everyday use.
  ３角形かくけいのすべての角かどの和わは１８０度どに等ひとしい。↗

  The sum of all the angles in a triangle equals 180 degrees.

For the geometric shape, use 三角 or 三角形; for the percussion instrument struck with a metal rod, use 「トライアングル」, which does not refer to the shape.

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

• 三角さんかくtriangle
• トライアングルtriangle (musical instrument)
• 三角形さんかくけいtriangle