I've been struggling to find the difference between those two structures, is one of them wrong or they are both right and have a difference in meaning/emphasis



2 Answers 2


の is a nominalizer, が is a subject marker, を is an object marker, and 見る is a plain transitive verb meaning "to see". 俺が走るのが見た is plain wrong because the act of running cannot see something.

  • ❌ 俺が走るの見た。(incorrect)
    ❌ My running saw [something].
  • 俺が走るの見た。(correct)
    [Someone] saw me running.

However, there is another verb 見える which means "to be visible", "to be in sight", "can be seen". This can take an action as a subject. See: What is the difference between 見る and 見える?

  • 俺が走るの見えた。(correct)
    [People] could see me running. / My run was visible.

You shouldn't view your sentence as

俺が走る + のを + 見た

Rather, it is

俺が走るの + を + 見た

From there, it is easily to see that の is just the 代名詞 that makes 走る(to run) into a noun 走るの(the action of running). The が and を are just being used normally here, and your sentence should be interpreted as such:

俺が走るの(The action of me running) を 見た(saw)。
(Someone) saw me running.

Obviously, "running" isn't a person and thus cannot see, 俺が走るのが見た wouldn't make any sense here. ("The action of me running saw???" What could an "action" see?)

P.S. you could, however, say 俺が走るのは見た. は does not specify it's the subject or object, but obviously it changes the emphasis(and thus the meaning to some extent) of the sentence by now making 俺が走るの the topic.

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