ꙮ tatybara ꙮ

A tangent is where a line meets a circle or curve, they touch where they're parallel. things don't overlap, they touch, and cram into the same space.

Additionally, "tangent" is often used to mean that two adjoining objects appear to be the same object due to angle, color, shape, line thickness and so on. If you're drawing comic panels, this can even occur between two adjacent panels, and your reader has to rescan the image to figure out why the arm of the guy in one panel becomes the bicycle of the person in the next panel.

You want to visually scan your own art to make sure this isn't happening accidentally, and reposition, color differently, alter lines, etc. when you spot it.