The sentence structure of "χρειάζομαι" and "Θέλω"
Hey everyone, do you always use the accusative case in these verbs? For instance, what does "I need a beer" and "I want a beer" mean?
In short, this is how cases work in Greek and how some pronouns in English retain this feature:
Nominative for the verb subject (e.g. he/she/who) - Αυτός έχει ένα μήλο = He has an apple.
Genitive shows ownership (e.g. his/her/whose, or of something) - Αυτό είναι το μήλο της Μαρίας = This is Maria's apple. (Nominative: η Μαρία)
Accusative for the verb subject (e.g. him/her/whom). - Βλέπω τον Πέτρο = I see Peter (him). (Nominative: ο Πέτρος)
Yes, that's right. One important thing to remember, though, is that if you follow χρειάζομαι with a verb, as in "να τρέξω", χρειάζομαι changes to the third person singular, ie "χρειάζεται να τρέξω". The meaning changes slightly from "I need..." to something like "It is necessary" (that I run, in this case).
If you're dealing with nouns, as D_ said, the object of a verb, the thing being affected by the action, takes accusative case.
Does it help if I say that Greek uses the accusative in pretty much the same way as German does?
ich brauche einen Hund
χρειάζομαι έναν σκύλο
(One difference is that prepositions in Greek are generally followed by the accusative, whereas many in German are followed by the dative, which no longer really exists in Greek.)
Yes, dative doesn't exist in modern Greek and it's largely been replaced by accusative. Where it does get confusing though, if my understanding is correct, is that for pronouns only, we use genitive for what would have been dative case. So, John gives the ball to George - Ο Γιάννης δίνει την μπάλα στον Γιώργο - both the ball and George are in accusative, that's straightforward enough. But then we'd have Ο Γιάννης του δίνει την μπάλα - George gives the ball to him. There, we use του (genitive) rather than τον (accusative).