Headstone and Landmark

Headstone noun - A shaped stone laid over or erected near a grave and usually bearing an inscription to identify and preserve the memory of the deceased.

Landmark and headstone are semantically related. In some cases you can use "Landmark" instead a noun "Headstone".

Landmark noun - A point in a chain of events at which an important change (as in one's fortunes) occurs.

Headstone and landmark are semantically related. Sometimes you can use "Headstone" instead a noun "Landmark".