first

In a sentence

• Dies ist das erste Buch, das ich gelesen habe.

  This is the first book I have read.

  Here, 'erste' is used as an ordinal number to indicate the position or sequence of the book being the first in an order.

• Ich möchte zuerst meinen Tee trinken, bevor wir anfangen.

  I want to drink my tea first before we begin.

  'zuerst' is used here as an adverb to indicate precedence in order or timing, meaning to do this action before others in time.

• Zunächst sollten wir die Grundlagen verstehen.

  First, we should understand the basics.

  The term 'zunächst' serves here as an adverbial phrase to provide sequence in actions or thoughts, indicating the priority in process or importance.