Why I should use on after rely, depend, and count.

Is there a reason? Or is it just arbitrary?

closed as off-topic by JJJ, jimm101, J. Taylor, Edwin Ashworth, MetaEd May 24 '18 at 15:23

This question appears to be off-topic. The users who voted to close gave this specific reason:

If this question can be reworded to fit the rules in the help center, please edit the question.


It's not a preposition in those cases, but a phrasal verb: you can't use the verb to rely without the on. The verb to count works on its own, but has a different meaning: to count on means to be able to rely on someone/something.

The examples you give are all linked to the semantic field of "support". Here you could argue that there is a physical sense of "something you can build on top of", so on would make sense metaphorically.

Ultimately, however, linguistic signs are arbitrary (de Saussure, 1916); language behaves rarely in a logical and consistent way, so there might well be no real reason for the choice.

  • Rely on, depend on, and count on are not phrasal verbs. Transitive phrasal verbs are subject to Particle Shift: I looked the book up/I looked up the book/I looked it up/*I looked up it. This doesn't happen with rely on: I relied on the book/*I relied the book on/*I relied it on/I relied on it. The on that appears with rely is just an arbitrary transitivizing preposition, and not a phrasal verb particle. Same kind of thing as the at in look at or the to in listen to. – John Lawler May 24 '18 at 15:10
  • I would disagree here; but I guess that depends on your definition of 'phrasal verb'. See for example usingenglish.com/reference/phrasal-verbs/count.html or macmillandictionary.com/dictionary/british/count-on – Oliver Mason May 24 '18 at 16:11
  • Indeed it does depend. Those are not sources for grammatical terms; they just use the term "phrasal verb" for any construction consisting of a verb with a following preposition-like word, without distinguishing types of such construction and their different grammars. This means that any grammatical rules they state about "phrasal verbs" in general are guaranteed not to apply to all phrasal verbs. Professional grammarians use more careful terminology, because they want to state rules that actually describe the language. – John Lawler May 24 '18 at 19:54

Most prepositions make perfect sense, see:


for example.

Some become more difficult as the concepts become more adult.

We rely on something because we expect it to be there in a supportive role, similarly for the others in your list.

Not the answer you're looking for? Browse other questions tagged or ask your own question.