Difference between "kaufen", "einkaufen", "aufkaufen" and "ankaufen"?

Question

I'd like to know: - What's the difference? - Which one needs *akkusativ-object*?

Answer 1

Here is a brief explanation of the difference between these terms.

"Kaufen" means to buy, in the most general and non-specific sense. "Einkaufen" means to shop, or to purchase something by shopping. As we would say, "I shopped for shoes today." "Aufkaufen" means to "buy up," or to purchase a lot or all of something. "Ankaufen" is used rarely. It means to "purchase", but also in the sense of to "acquire", as we would say in English that someone "acquired" a piece of land. Ankaufen is not commonly used, at least to my knowledge.

All such verbs will take the accusative.