erzählen

Erzählen (to tell, to recount) is a regular weak verb: ich erzähle, du erzählst, er erzählt, wir erzählen, ihr erzählt, sie erzählen. The simple past is erzählte. The past participle is erzählt with no ge- prefix, because the inseparable prefix er- blocks it. The perfect takes haben: er hat mir alles erzählt (he told me everything).

The verb takes two objects at once, and their cases differ. The person you tell goes in the dative, and the thing you tell goes in the accusative: ich erzähle dir eine Geschichte (I am telling you a story). Getting dir rather than dich here is the main grammar point to practice.

German separates several verbs that English lumps under "to tell" and "to say". Erzählen means to narrate something at length: a story, a joke, what happened at work. Sagen means to say a specific thing: sie sagt, dass es regnet (she says it is raining). Reden and sprechen both mean to talk or speak, describing the activity rather than the content.

The verb is related to zählen (to count), and the connection survives in English too, where "to tell" once meant counting, as in a bank teller.

Useful related words: die Erzählung is a story or short narrative, der Erzähler is the narrator, and erzähl mal! is a casual way to say "go on, tell me".