This is the 830th most frequent German word.
kaufen
To buy.
The verb 'kaufen' is conjugated in the first-person singular present tense to denote an ongoing or habitual action of buying.
Ich kaufe ein Buch.
I buy a book.
Here, 'kaufen' is used in the past tense (perfect tense in German), indicating a completed action in the past.
Wir haben gestern ein Auto gekauft.
We bought a car yesterday.
In this sentence, 'kaufen' is used in the infinitive form in combination with the modal verb 'müssen' to express necessity.