Landmark and Point of no return

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

Point of no return and landmark are semantically related. In some cases you can use "Point of no return" instead a noun "Landmark".

Point of no return noun - A line that when crossed permits of no return and typically results in irrevocable commitment.

Landmark and point of no return are semantically related. Sometimes you can use "Landmark" instead a noun phrase "Point of no return".