A: "I assume you know how this works."
B: "I am assuming you know how this works."

So if you expect someone to know how to use a certain machine for instance could you say either of the too? I cant make out a difference in meaning so if there is none which would be the preferred choice for most speakers?

  • 2
    There is a slight difference, in the usual way, the progressive tense indicates current action. The first sentence might be said before any action is taken, possibly implying you want the other person to take an action. The second version might be said if you are in the middle of using the machine and are about to pass over control to the other person.
    – SteveES
    Apr 20, 2017 at 16:42
  • 1
    The 'ing form refers to ongoing activity. In your example, I can't see any practical difference in application. But the nuance would be this. "I assume you know how this works" stipulates an assumption and moves on. "I am assuming you know how this works" implies an ongoing concurrency between their knowledge and each thing you explain. I can't think of a way in which there is really a difference in meaning in this example.
    – fixer1234
    Apr 20, 2017 at 16:47
  • 1
    It occurred to me that there is a slight style difference. "I am assuming" would be a neutral way to state that what you are about to explain reflects an expectation of certain knowledge on their part. "I assume you know" could be perceived as having a "value" weighting, like this is something I expect you should know. You are making sure that you won't be wasting your time explaining something to an unprepared person, and if they actually don't know, it's rude of them to be wasting your time, or they are stupid because they should know but apparently lacked the intelligence to absorb it.
    – fixer1234
    Apr 20, 2017 at 16:56

1 Answer 1


I assume you know how this works.

You are about to start something - you want to make sure the other person knows how this works before you start.

I am assuming you know how this works.

You are starting an action under the assumption the other person knows how this works, and are retroactively making sure that your assumption is correct.

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