noun, noun which may take the genitive case particle 'no'
tangent line; tangential line
Geometry term for a line that touches a curve at exactly one point without crossing it.
円の接線を引いてください。
Please draw a tangent line to the circle.
曲線の接線の傾きを求める。
Find the slope of the tangent line to the curve.
From 接 (contact, touch) + 線 (line), literally 'touching line'.