Tangential (adjective)

1. Relating to or touching a curve or curved surface at only one point, but not intersecting it.
2. Not closely related or pertinent to the main topic; digressing.

Origin:

From latin tangent- "touching", from the verb tangĕre "to touch".

Examples:

1. The tangential angle was used to calculate the slope.
2. The tangential force was calculated by the formula.
3. The tangential velocity was measured.
4. His comments were tangential to the topic.
5. His answer was tangential to the question and not relevant.