What is the difference between "doing something" and "on doing something"?
I don't understand the difference between "doing something" and "on doing something". I am going to make up a few examples.
(1) On cleaning up my bedroom, I found my valuable watch.
(2) Cleaning up my bedroom, I found my valuable watch.
Do these sentences have the same meaning? Please explain it. Thank you very much.
They don't have the same meaning at all.
- The preposition on is used as a function word to indicate an instant when something begins or is done according to Merriam Webster definition No. 3. Therefore, No. (1) sentence could be rephrased to
As soon as (The moment) I started to clean up my bedroom, I found my valuable watch.
- No. (2) sentence could be rephrased to
When I Cleaned up my bedroom / While I was cleaning up my bedroom, I found my valuable watch.
"Cleaning up my bedroom" is called participle clause or absolute clause (construction). You can visit the links and see how they work.
Pretty much the same meaning, I'd say. Both have implied additional words:
[Upon] ... cleaning up my bedroom, I found my valuable watch. or On [the occasion of] cleaning up my bedroom, I found my valuable watch.
[While] [c]leaning up my bedroom, I found my valuable watch.