I think the examples on this page are clear: https://en.m.wikipedia.org/wiki/Cot%E2%80%93caught_merger https://en.m.wikipedia.org/wiki/Cot%E2%80%93caught_merger

I think the examples on this page are clear: https://en.m.wikipedia.org/wiki/Cot%E2%80%93caught_merger https://en.m.wikipedia.org/wiki/Cot%E2%80%93caught_merger where cot/caught is the same difference as don/dawn.