The nominative, genitive, dative, and accusative cases as we know them in english are cases used for certain structures of sentences. When using the accusative case, we ask, "Doing what?" For the dative, "For who/whom?" and so on. In the most basic sense, the four words just mean their respective cognates, the four cases. English speakers don't use the cases as they seem to just say things in the most comfort possible. For more information on how the cases affect German sentence structure, there are multitudes of websites and even online textbooks to skim over on the subject. Hope this helped!
"Die Frau ist ein Apfel" would be "The woman is an apple" (potentially insulting), and would sound exactly the same if spoken. Accusative case comes in to save you from your faux pa and the "ein" becomes "einen", changing the meaning of the sentence to something less antagonistic.
I hate to be a Besserwisser here, but there is another distinction between the nominative and accusative sentences other than ist/isst and einen.
In the standard language, Mensch becomes Menschen in the accusative singular, as it is one of the nouns belonging to the so-called N-declension (in other words it takes the weak declension).
- Die Frau isst einen Menschen.
You can check the Duden (official German dictionary) page for yourself if you'd like:
If you're confused about the concept, I wrote an explanation a few months ago:
Edit: I forgot to mention that in the colloquial language, Mensch is sometimes left uninflected, einen Mensch. Although this is technically incorrect (and should not be attempted in the written or formal language), people probably wouldn't notice if you leave out the suffix in casual speech.
There is - as the others mentioned - no real continuous form in German. That might make it easier for you (one of the very few easy things in German), because you can always translate into: Sie isst einen Apfel. If we want to make sure that it is an ongoing process we are watching right now, we almost always would use "gerade" (just now): Sie isst gerade einen Apfel". "Der Postbote kommt gerade". (The postman is coming). This "gerade" would follow the verb immediately.
Please excuse my typo jn the last comment; that should be "eating", not "eatinf". In addition, I'm still in the same lesson and just had another ezercise that was "Ihr essen einen Apfel" and the translation was "You are eating an Apple". Are there times where it's just considered nonsensical to translate it just as "eat/eats" in English and has to be "am/are eating"?
No. It's for the accusative case. When something is the verb "receiver" of the verb. Die Frau is nominative, einen Apfel is accusative, it's the thing that's being eaten. Only masculine articles change in the accusative case: ein - einen, der - den. Not all 'ein's will take that though, neuters stay the same as they're not masculine obviously.
No it wouldn't. Germans don't normally say something like Eine Kartoffel esse ich. They might put other parts in front though. For example, instead of Ich esse eine Kartoffel in der Küche, one could say In der Küche esse ich eine Kartoffel. While those things are gramatically correct, they're not used with simple things like my first example because ambiguity is possible and it sounds, even to them, a bit outlandish.
Edit: I might've missed part of your question. Isst and ist can almost always be figured out from context. In spoken German, ist may be said a bit shorter than isst.
I think you're misunderstanding the concept. The word Apfel itself is not any case, it is in the accusative case in this sentence as it is the direct object of the sentence. This is not completely foreign to an English speaker, for example: I and he are nominative, in other words the subject of the sentence; me and him, on the other hand, are accusative, in other words the direct object. English has of course lost its case system, but pronouns are a living remnant of it.
- Der Mann (nominative) sieht den Briefträger (accusative) - The man (nominative) sees the postman (accusative).
- Er (nominative) sieht ihn (accusative) - He (nominative) sees him (accusative).
No, the article declension has nothing to do with whether the following letter is a vowel. The masculine ein becomes einen when it's followed by the accusative object of a sentence. Remember, ein only becomes einen if it's a masculine ein. Neuter nouns also take ein but stay the same in the object.
Ich sehe einen Apfel auf dem Tisch. - I see an apple on the table.
Here, Apfel is the accusative object of the sentence. What is receiving the action of seeing? An apple.
Ein Apfel fällt vom Baum. - An apple is falling from the tree.
Here, Apfel is the nominative subject of the sentence. What is performing the action of falling? An apple.
By the way, the order is not always set, and can be moved around. For example, even though Apfel comes at the end of the sentence, the answer to the question "what is performing the action of falling?" is the same: an apple - so the case stays the same.
Vom Baum fällt ein Apfel. - From the tree falls an apple.
I hope this helps. Viel Erfolg! :)
Accusative requires a direct object. Dative requires an indirect object. Genitive shows possession. Of course all cases exist in English, but with little to no inflection,at leat not in presend day English. English dropped all the difficult inflections of cases and such compared to its earliest form, but German has kept all of them, that's why learning German is a bit challenging at first.