A scar is the mark left on our skin after a wound has healed, or on our mind after an unpleasant event. If I were to show you a photo of my operation scars* while the staples were still in, I reckon you'd be scarred (and maybe scared too)
A scar also the mark left on a plant stem after a leaf is removed. Plants can be scarred deliberately, by scratching them. When I was a kid, my dad scratched my and my brother's names on tiny marrows in letters so small we couldn't see them until the fruit swelled and the scars were clearly visible.
A scar is also a steep cliff or outcrop of rock. I think the word escarpment may be connected, but I'm not sure. I'm also not sure if this bit of rock is actually a scar**, but it's a nice picture isn't it?
*It was a long time ago, there's not much to see now.
** Geography was never my strong point.