What is the difference between "on doing", "by doing", and "in doing"?

A difficult point to French learners of English as in all three cases, you would say "en faisant".

Example sentences, taken from the Longman Dictionary of Contemporary English:

What was your reaction on seeing him?

Howard had put his own life in danger in trying to protect the Queen.

She earns her living by selling insurance.

  • 1
    Please visit English Language Learners
    – Kris
    Commented Dec 5, 2013 at 12:47
  • Prepositions are typically weak meaning words, in the sense that some can be interchanged with little loss in meaning.
    – tylerharms
    Commented Dec 5, 2013 at 13:06
  • And also correspondences between the usages of French say and English prepositions are not one-to-one but often fairly unpredictable. Commented Dec 5, 2013 at 15:22
  • Ok, got it, Kris. So, I will save my trickiest questions – where even native speakers of English might be at a loss – for this website and ask the others on the website you redirected me to! Provided I can work out such questions…
    – user58319
    Commented Dec 5, 2013 at 16:33
  • Of course, Edwin. Would not life be dull if languages allowed for (?) literal translations… !
    – user58319
    Commented Dec 5, 2013 at 16:42

1 Answer 1


The difference between "on leaving" on the one hand and "by selling" and "in trying" on the other hand is easy: "on leaving" is to do with time and means "when you saw him", whereas "by selling" and "in trying" are to do with the cause and effect relationship. But there is a difference: by = she sells insurance in order to earn a living, it is her aim, it is a means to an end; in = Howard does not try to protect the Queen in order to put his own life in danger, it is just an occupational hazard for bodyguards, a side effect.

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