jump on/onto

1. A dog jumped on the jetty.
It can mean both of:
"A dog was on the jetty and jumped there"
"A dog jumped toward the jetty and landed on it"

2. A dog jumped onto the jetty.
It can mean only:
"A dog jumped toward the jetty and landed on it"

paco

Paco, I would just change your distinction a little bit. Instead of jumping toward the jetty, the dog, beginning from a position that is not on the jetty, jumps toward the jetty and lands on it. Merely jumping toward the jetty could result in something other than landing on it, especially if the dog misjudges the distance.

Davkettespecially if the dog misjudges the distance.

Thank you, Davkett. Yes, you are right. I, a dog, might misjudge the distance.

Hello Paco,

Thanks for valuable thoughts.

One thing I want to know that

1. A dog jumped on the jetty.
It can mean both of:
"A dog was on the jetty and jumped there" (IF I leave this one).
"A dog jumped toward the jetty"

2. A dog jumped onto the jetty.
It can mean only:
"A dog jumped toward the jetty"

Yes, you are right.
Sometimes native speakers use "jump on" in the same meaning as "jump onto".
It is the reason why we are confused with the two expressions.

paco