For-On | Commonly Confused Words

For

/fɔː(r)/

Used to indicate a purpose, cause, destination, or reason for something.

There's a letter for you.Take care of yourself, for he means to kill you."For it was summer – late June.

This word has no antonyms

/ɒn/

Indicating a position touching or in contact with the surface of a place or object

I think the wallet is on the table.From then on she took control of everything.He turned and put his hand on Silver Blaze is back.

This word has no antonyms

For often indicates benefit, purpose, or a duration of time.
On is used to denote position or contact with a surface.
Think of for as something that is in favor or in purpose of an action or event.
On can be remembered as being atop something or specific dates, like being on a day.
For often deals with the duration or intended purpose, where On is more precise, about location or time.