犬が死んだ
犬は死んだ
は is typically used to mark something already in context as the topic. Would that be equivalent to "The dog died" since "The" typically marks something know?
が is a bit more confusing for me. Would it be more accurate to translate this to "A dog died"? I've also heard が is used to speak about things you currently witness. So I feel like in this regard it can also mean "The dog died".
Can anyone clarify how to translate sentences like the above where only the particle differs?
Unfortunately, you cannot simply think "は is the and が is a(n)". This may sound confusing, but "The dog died" has to be translated into Japanese either as 犬は死んだ or 犬が死んだ depending on the context, even in a situation where everyone knows which dog "the dog" refers to.
For example, let's say you and your family recently bought a dog from a pet store but have not yet given it a name. If that dog suddenly died today, you have to call your family at work and say "犬が死んだ!" using が. If you used は in this situation, you would sound awfully unnatural. For the reason, please read the following questions.
が has another usage known as exhaustive-listing, so "It's the dog (but not that cat) that died" is one of the possible interpretatins of 犬が死んだ. But opportunities to say something like this would be very limited, of course.
I am simply learning Japanese, so I don't claim to know for sure; but Tae Kim has a good article on this topic.
Based on this, I would suggest:
犬は死んだ -- The dog died
犬が死んだ -- The dog is the one that died.
Another way to think about the difference is to view them as answers to particular (albeit nonexistent) questions:
Notice that the focus is different in each question (and therefore, the answers too). The first is focusing an event surrounding the dog; the second, on the details surrounding a death. @InTheProgress also mentions this at the start of their 2nd paragraph.
