Subject and Object in a 太ってる sentence

Question

I've never really had to think about object vs subject in native English since it's always come naturally for me, and I barely remember grammar studies when I was a child.

It seems to be important to mark subject and object properly in Japanese so I'm trying to understand how it works in the following example:

ばいきんまんを太った。

Is Baikinman the object here since "got fat" was the action that happened to him? Baikinman is the receiver of the action of getting fat?

ばいきんまんが太った。

Or is Baikinman considered the subject? If that's the case then what would be the object here? If nothing is acting on him becoming fat?

Can someone explain this in simple terms for me?

Answer 1

If you're having trouble with subject, object and transitivity then 太る is probably not a good verb to start with since it does not map to a verb in English.

太る is an intransitive verb (does not take an object) which means 'to become fat'. Putting this in た form means that the process of becoming fat is complete, i.e. 'got fat'.

I think the fact that you translate this with 'got' may be confusing you because in the sentence 'X got Y', X is the subject and Y is the object. But this 'got' has a different meaning from the one you are using above. When you say 'I got soup' you mean 'I obtained soup'. When you say 'I got fat' you don't usually mean 'I went out and bought some fat'. You mean 'I became fat' and that 'became fat' is all neatly swept up in the single word 太った so there is no place for an object.

Answer 2

I agree to the comment by user3856370, especially about transability in Japanese. But I would like to list some more examples which will be useful to non-native speakers.

• ばいきんまんを太っている。ばいきんまんを太った。(both sentences are ungrammatical)

• ばいきんまんを太らせる。(literally, make Baikinman fat, 太らせる is a transitive verb)

• ばいきんまんは太っている。ばいきんまんが太っている。(both are grammatical)

• ばいきんまんは太った。ばいきんまんが太った。(grammatical in past tense)