Translation guide
A triangle is a shape with three sides. In Japanese, the basic word is 三角形 (さんかくけい), but in everyday conversation, 三角 (さんかく) is more common. There are also specific terms for different types of triangles and related concepts.
Referring to the shape with three straight sides and three angles.
The most common, everyday word for 'triangle'. Used in casual conversation, for shapes, and in compounds like 三角定規 (triangle ruler).
この形は三角です。
This shape is a triangle.
三角に折ってください。
Please fold it into a triangle.
The formal, mathematical term for 'triangle'. Used in geometry, textbooks, and technical contexts.
三角形の内角の和は180度です。
The sum of the interior angles of a triangle is 180 degrees.
The symbol △ is read as さんかく and is used in writing, such as in marking tests or indicating a triangle shape.
答えが合っているものに○、間違っているものに△を付けてください。
Mark correct answers with a circle and incorrect ones with a triangle.
Describing specific kinds of triangles based on sides or angles.
Referring to things that are triangular in shape, like a musical instrument or a road sign.
The musical instrument (triangle). Borrowed from English.
トライアングルを鳴らす。
Play the triangle.
Triangular road sign, such as a yield sign.
前方に三角標識があります。
There is a triangular sign ahead.
A relationship involving three people, often romantic.
Love triangle. The standard term for a romantic relationship involving three people.
彼らは三角関係に陥った。
They got caught in a love triangle.
三角 (さんかく) is the everyday word for a triangle shape, while 三角形 (さんかくけい) is the formal geometric term. Use 三角 for casual descriptions and 三角形 in math class or technical writing.
机の上に三角の折り紙がある。
There is a triangular origami on the desk.
三角形の面積を求めなさい。
Find the area of the triangle.
Isosceles triangle. Two sides are equal.
二等辺三角形の底角は等しい。
The base angles of an isosceles triangle are equal.
Right triangle. Has one 90-degree angle.
直角三角形の斜辺を計算する。
Calculate the hypotenuse of the right triangle.
Obtuse triangle. Has one angle greater than 90 degrees.
鈍角三角形は一つの角が90度より大きい。
An obtuse triangle has one angle greater than 90 degrees.
Acute triangle. All angles are less than 90 degrees.
鋭角三角形はすべての角が90度未満です。
An acute triangle has all angles less than 90 degrees.
A triangular corner shelf or rack, often used in kitchens.
三角コーナーにスポンジを置く。
Put the sponge in the triangular corner rack.