"I can speak Japanese."
this sentence literally reads as "nihongo ga hanasemasu". the reason that は is pronounced like "ha" not "wa" in this sentence is because the は is part of the verb はなす (話す, hanasu = to speak). 「はなせます」literally means "can speak".
は is pronounced as "wa" when it's the topic particle as sierraw13 has already commented. が (which isn't part of はなせ) is the identifier particle. these are concepts that are pretty difficult for native english speakers to understand (myself included) so i'd look them up to gain a better understanding (i still haven't wrapped my head around them). but i know if you change them in certain sentences it can alter the meaning. like this:
私はジョンです (watashi wa jon desu = i am john)
私がジョンです (watashi ga jon desu = i am john)
they translate as the same thing but they have different implications. in the first sentence, the important part is that you are john. it's sort of like saying "as for me, (i) am john". that's how i've seen others describe it. on the other hand, the second sentence, the important part is that you are john. this would probably be in response to a question such as "who is john"?
i think が is used here because the sentence involves a potential form of the verb (i can speak japanese), but it would be nice if someone could clarify that.
では is another such particle that's really a combination of two other particles. you've probably seen では in ではない (de wa nai) or ではありません (de wa arimasen), which both mean "am not", "are not", "is not", etc. in this case, the は is pronounced as "wa".
in summary, は is pronounced "wa" when it's used as a particle & "ha" for anything else.
sorry if this is a little confusing as i'm still learning too. hope this helps :)
The reason は is pronounced 'wa' when used as a particle is because of historic pronunciation. This is a good explanation: https://japanese.stackexchange.com/questions/379/why-are-the-particles-は-ha⇒wa-へ-he⇒e-and-を-wo⇒o-not-spelled-phonet
Why the heck do they throw in a phrase in Potential verb form, already in a tier 4 assignment? We have hardly even touched verbs in their default present form at that point. It took me very long trying to figure out why it was not 日本語がはなします and how the i was suddenly turned into an e. 話す to 話せる
Isn't there supposed to be some logical progression to how we first learn to use simple verbs in their most basic forms, then you add more complex verb forms such as the potential form?
Anyway, for anyone else who got stuck wondering what is going on in this sentence, this page was helpful to me:
I think that the ap LingoDeer has a good info page on this in their second lesson, but it only states that the pronunciation is changed and does not really say why either. I have been using both aps because that one seems great for sentence structure, and this one feels less painfully dragging.
There's several answers in this thread:
If none of those help, can you let us know what you still find confusing, and hopefully someone can help clarify?
はなせます ("can speak") is an intransitive verb. It doesn't have a direct object and thus doesn't take を. You're not actively saying that you're doing the action of speaking, you're just stating that you have the passive ability of being able to speak.
If you used はなします instead ("speak"), that would be the active form and would have a direct object and a を. はなせます is called the "potential form" of はなします, because you're saying that you have the potential to speak, not that you're actually speaking.
This is a little confusing for non-native speakers (myself included), but が indicates the subject of the sentence, and は indicates the topic of conversation. In this sentence, the topic of conversation is (probably) not the Japanese language, so we don't use は here.
See mfazzolari's explanation above for a better (and more detailed) explanation.
As a side note, 「日本語を話せます」 is also an accepted answer (minus the quotation marks).
So hear me out. The full sentence would look like わたし (は) 日本語 (が) はなせます.
は describes the overarching topic of what is being discussed and in this sentence, you, the speaker, are the topic. It's implied so we don't have to say it in conversation, but it is there, just hidden.
But now that we know that you are the topic, what are you doing? What is happening to you? How can we describe you? One usage of が that I've noticed is to make a specific and direct connection between things. In this case, it directly links "japanese" to the verb "can speak" to make the complete thought "(the overarching topic) can speak japanese".
As for the reason why it's が and not を, RVJoWts did a great job of explaining that. Hope this helps. Sorry if it's confusing
You have to include 私 when the subject (or topic of conversation) isn't obvious. In this example, the subject is /technically/ the Japanese language (because it has a が), but it's gathered from context that the speaker is referring to themselves.
This is also why it's unnecessary to include 私 in sentences such as the following: 「ジョンともうします」 「おちゃが好きです」
For similar reasons, あなた is excluded in sentences where the listener is clearly the subject: 「英語をはなせますか？」
(Please note that the above examples have replaced several kanji with their hiragana readings.)
を is the grammatically correct particle to use with the regular form of the verb: 英語を話します (eigo o hanashimasu, I speak English). が is the grammatically correct particle to use with the potential form: 英語が話せます (eigo ga hanasemasu, I can speak English). Some native speakers have started using を with the potential form, though.
In the が + potential construction, the focus is on the noun.
新聞が読める (what I am able to read is newspapers [as opposed to other written media])
ここで切符が買えますか (is this where tickets [as opposed to other items for sale] can be bought?)
In the を + potential construction, the focus is on the entire phrase.
新聞を読める (what I am able to do is read newspapers)
ここで切符を買えますか (is this where I am able to buy tickets [as opposed to doing some other action]?)
を + potential is not yet considered standard, but has begun to gain acceptance among some speakers.
(Paraphrased from Japanese: The Spoken Language)
If you check the previous comments there are already some good explanations: