Learn English – use assist as a synonym of attend

Is "assist in" the same as "assist with"? Can I always substitute the one where the other is used, or is there a difference in meaning?

In general, they're pretty similar and frequently interchangeable -- at least one-way. (You can say "assist with" for "assist in," but you should be careful swapping "assist in" for "assist with," since there are some nuances.

If you "assist in," it may indicate a longer-term and/or more in-depth assistance -- the senior academic meeting with the junior one daily over a course of months, for instance.

If you "assist with" something, it can indicate a much shorter-term, or "shallower" form of assistance -- you aren't going around asking questions to help the police, but are instead answering the questions the police gave. (If you said "I am assisting in the police inquiries," you would be presumed to be doing a share of the work.)

So you can assist your co-worker with a project, or you can assist your co-worker in his work, and it means pretty much the same thing. (Though even there, notice the nuance: a project is a thing with an end, while "his work" is more open-ended!) But you want to be careful saying you're assisting the police in their investigations unless you mean that you're doing more than just answering a few questions.

However, even if you use the "wrong" in/with, a sentence in context will usually be interpreted the correct way.

(Native American English speaker here.)

With one possible exception, I don't think I've ever heard an American say “dodgy”, and this includes Americans who deliberately include bits of British English in their speech as an affectation. For example, Americans I've known who say “petrol” don’t say “dodgy”. However, I think most Americans I know personally would understand “dodgy”, especially in context. And if someone wanted to fake a British accent, some might well go out of their way to use the word “dodgy”, though probably not all of them would think to use it.

The one possible exception is an American housemate I had on long trip to Scotland last year. I can't remember for sure if she said “dodgy”, but in six weeks, she had unwittingly picked up some Britishisms, including “got it sorted”. “Dodgy” seems pretty easy to pick up unwittingly.

I certainly do hear “dodgy” from British friends and co-workers all the time. I think I'd use the word with them without it seeming like an affectation.

Other Americans' experiences will be different, of course.