I know this can be flagged as off topic, because it a bit broad, but let me give it a try. Is there any difference between these phrases:
- on the verge of
- on the edge of
- at the verge of
- at the edge of
Suppose that you want to say, something is at the boundary of two opposing states, like the country was at the edge of chaos.
I've checked the dictionaries and I honestly think all of them are interchangeable. However, it seems "on the edge of" is far more common among the four according to Ngram: