Could anyone help me with finding the difference between saying "catch a bus/train/etc" and "take a train/bus/etc"? I'm afraid I haven't been able to glean one from my dictionary.
Catching a bus describes the process of getting to a stop/station, waiting and boarding.
Taking a bus describes the entire process, including the journey itself.
Much of the time, the distinction isn't important. For example:
However, it could be relevant:
It is a similar meaning to catch as catching a fish, or catching a ball. You and the bus are apart, and then you bring yourself into contact with it through your own effort. If you try to catch a bus, and fail, you miss it.
One other thing, you catch a bus at a specific place:
But you take the bus from a place:
In American English, "take" is usually premeditated -- you made plans to be at the stop at such-and-such time, bought a ticket in advance, etc. "Catch" has more of an "in the moment" sense -- you had started to walk to work but caught a bus that was going by, for example.
For British English, see the comment from @slim.
The meaning common to "catch" and "take" in these idiom is "travel by". And there is very little difference. If there is one, it's in the tone. "Take" implies you have control over the mode of transportation; "catch" implies you have to fit your schedule to it. So if you were writing fictional dialog, a more dynamic character might "take" whereas a more passive character might "catch".