What's the difference between -ga and -o when they are used to designate a direct object?

Question

During the past month I've been addicted to Japanese. I've listened to about 10 online tutorial video courses and read about as much printed lessons. I am determined to learn Japanese, but I am really a newbie so my question may be very basic, but please bear with me.

If I understand correctly, both -ga and -o particles designate a direct object. For example, I've heard:

Watashi wa ongaku-ga suki desu. = I like music

Watashi wa ongaku-o kiku (or kikimasu, I'm not sure) = I am listening to music

So why is it ga in one case and o in the other? Is it specific to the verb or the object or what?

P.S. I don't know hiragana yet, so I'd appreciate if you could keep your examples, if any, in romaji.

Answer 1

It depends not only on the verb, but on the form of the verb.

The general rule is that static verbs and adjectives take "ga" and "action verbs" take "o" on the direct object.

piano-o hiku
play the piano

piano-ga hikeru
can play the piano

Here, playing the piano is an action, thus "o" is used. Being able to play the piano is a state, thus "ga" is used.

ringo-ga hoshii
want an apple

ringo-o hoshigaru
act like you want an apple

Again, to want an apple is a state, so use "ga", to act like you want it is an action, so use "o".

Answer 2

This is not as much of a newbie question as you might think. dainichi gave a good general rule-of-thumb, but at the risk of confusing you, I'd like to point out that there are many cases when を and が are actually interchangeable. For example, the sentence "I can play the piano" can be written either

ピアノが弾【ひ】ける
piano ga hikeru

or

ピアノを弾【ひ】ける
piano wo hikeru

A psychology professor from Ritsumeikan University in Kyoto conducted a study on the interchangeability of を and が in 2006. Although the paper he wrote is mostly in Japanese, there is a good summary in English at the beginning. He found that when presented with the sentence

ピアノ __ 弾【ひ】ける
piano __ hikeru

college students were split almost 50/50 on filling in the blank with を vs. が, while older people more strongly favored が.

The main point the author makes is that in sentences where the predicate is an action, e.g.

ほしがる
hoshigaru
to want (or as dainichi more aptly put it, to act like you want)

the use of を is overwhelmingly favored over が; while in sentences where the predicate describes a state, を and が are either interchangeable, like with

弾【ひ】ける
hikeru
to be able to play (an instrument)

or が is strongly favored, like with

好【す】き
suki
to like

The author also points out that context is important. Even though を and が are more or less interchangeable in the sentence

ピアノ __ 弾【ひ】ける

を was heavily favored in the sentence

練習【れんしゅう】して，彼【かれ】はピアノ __ 弾【ひ】けるようにした
renshuu shite, kare ha piano __ hikeru you ni shita
He practiced and tried to become able to play the piano. (awkward translation but you get the gist)

However, even with this sentence, roughly one-third of the older respondents chose が, so you're unlikely to go wrong if you always select が when the predicate describes a state rather than an action.

This is just a slightly more nuanced version of the rule that dainichi gave. I simply wanted to point out that most rules have exceptions, and in the case of を versus が, even native speakers do not always reach a consensus.

Answer 3

Isn't there also a difference depending on whether the verb is transitive or intransitive?

eg.

電気を消す。

Turn off the lights.

電気が消える。

Lights turn off.

Intransitive verbs tend to follow ga while wo preceeds transitive.

Answer 4

Althouh a (rare?) verb 好く (suku) exists, "suki" is an adjective (borrowed from Austronesian, therefore uses -na instead of -i: "suki-na hito" instead of "suki-i hito"), and "suki" can also be a noun ("fondness"). By they way, suki derives from suku according to Wiktionary.

Watashi-wa	ongaku-ga	suki	desu.
I-TopicMarker	music-SUBJ	pleasing	be

is literally

"As for me (wa=set the context), music (SUBJECT) is liked/likable/lovable/pleasing (adjective)". The only verb here is desu.

When we translate, we need to find the most similar word. But if a word is an adjective in English, then it doesn't mean that the most similar word in an other language is also an adjective.

For example, word "like" is used differently in other languages:

• in English the transitive verb is used ([subject=liker] likes [object of liking]). Also could be a noun: "You are my love"... well, love≠like, but the meanings are similar.
• in Russian it's a reflexive verb and in Spanish it's an intrasitive verb, for both the (kinda) order is reversed:

la música	me	gusta
SUBJ	INDIR.OBJ	VERB.INTR

music	pleases	me
SUBJ	VERB.TR	DIR.OBJ

music	is	pleasing	to me
SUBJ	VERB	ADJ	INDIR.OBJ

• rarely in colloquial Russian an adverb is used (although I never use this "по нраву"):

muzyka	mne	po nravu
SUBJ	INDIR.OBJ	ADV

• in Japanese it's an adjective, therefore use が (of course sometimes you need は instead).

Same with hoshi-i (it is actually "desirable" instead of "to want"; from obsolete verb "hor-u") and kira-i ("disliked"/"hated"; from kira-u).

Although if you add suffix -garu to an adjective, you would get a verb (as it's done in two accepted answers), so since it's a verb now you should use を. I said "should" insead of "must" because according to the answer that mentions the paper, a minority prefers が with -garu (maybe they still feel it's an adjective?).

TL;DR: Use only Japanese (not English) grammar to find out whether it's a verb or an adjective, and to find the direct object in a Japanese sentence.

Answer 5

hiku is a dictionary form of verb which means play [for instruments, e.g. piano, guitar etc.] verb ending in ku can be changed to potential form by changing u to e and add eru so that hiku becomes hikeru [can play]. Watashi wa piano ga hikeru.[I can play the piano.] I think the appropriate particle here is ga.Watashi wa piano ga hikeru koto ga dekimasu.[in other potential form]