"I have a plate."
Translation:Ich habe einen Teller.
Because the gender of "Teller" is masculine, and therefore in the accusative case it must be "einen".
Although this might be a true (but uncommon) translation, 'Teller' is the word you really should use. 'Platte' could also mean 'sheet' or 'panel'.
Die Platte does not mean "plate" as we use it in English (even though there is an obvious etymological connection). "Die Platte" refers more to a platter or a long sheet of something used as a cover. We incidentally use the word "plate" in the same circumstance, as in: a steel plate covered the electrical circuitry. If one is to say plate in the sense of something that one eats food off of, then "der Teller" is the way to go.
Since the noun is an accusative masculine noun, you would use einen. If it was feminine it would be eine and if it was nominative masculine, it would be ein
It's in accusative because the verb "haben" takes direct objects. Ich is in nominative, thus the subject, therefore Teller must be in accusative.
Figuring out the correct cases (nominative, accusative, etc) is downright mindboggling for me. Does anyone have any good references they're willing to share on learning this better?
I had 'einen' and then changed it to 'ein' at the last minute...any tips or additional resources would be greatly appreciated.
There is a very easy way to navigate your way through the accusative case. The trick is to reference the verb being used in the sentence. Verbs that take direct objects (transitive), will impart the accusative case. For example, verbs like have, eat, or drink all take direct objects. I have A PEN. I eat AN APPLE. I drink THE COFFEE. In other words, verbs that do something to an object will impart the accusative case in German. So Ich habe EINEN KUGELSCHREIBER, Ich esse EINEN APFEL, ich trinke DEN KAFFEE.
On the other hand, verbs that do not take direct objects do not impart the accusative case. Verbs like go or stay will not have a direct object in German. You cannot GO SOMETHING, nor can you STAY SOMETHING. Hence these verbs do not impart the accusative case.