分度器(ぶんどき)

分度器(ぶんどき) is a protractor, a semicircular tool marked in degrees used for measuring and drawing angles.

ETYMOLOGY:
分度(ぶんど) (dividing degrees) + 器(き) (instrument).

COMMON EXPRESSIONS:

• 分度器(ぶんどき)で測(はか)る: to measure with a protractor
• 分度器(ぶんどき)を使(つか)う: to use a protractor
• 分度器(ぶんどき)を当(あ)てる: to place a protractor (against something)

RELATED GEOMETRY TOOLS:

• 定規(じょうぎ): ruler
• 三角(さんかく)定規(じょうぎ): set square / triangle ruler
• コンパス: compass (for drawing circles)
• 直定規(ちょくじょうぎ): straightedge

USAGE CONTEXT:
Introduced in Japanese elementary school math (算数(さんすう)) when students learn about angles. Part of the standard 文房具(ぶんぼうぐ) (stationery) set for geometry.