dreizehn
thirteen
The cardinal number that follows twelve; the number 13.
Das Buch hat dreizehn Kapitel.
The book has thirteen chapters.

thirteen
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thirteen
The cardinal number that follows twelve; the number 13.
Das Buch hat dreizehn Kapitel.
The book has thirteen chapters.

The number 'dreizehn' (thirteen) is made up of 'drei' (three) and 'zehn' (ten). This pattern applies to all numbers from 13 to 19: first comes the ones digit, then 'zehn' (ten), e.g. 'vierzehn' (fourteen), 'fünfzehn' (fifteen).
Der Zug hat heute siebzehn Minuten Verspätung.
The train is seventeen minutes late today.
Pay attention to the stress so you don't confuse 'dreizehn' (thirteen) with 'dreißig' (thirty). Normally, the first syllable is stressed: DRÉIzehn. In 'dreißig' (thirty), the stress is always on the first syllable: DRÉIssig.
Ich bin dreizehn Jahre alt, nicht dreißig.
I am thirteen years old, not thirty.
The idiom 'es schlägt dreizehn' (that's the limit / enough is enough) is a fixed unit. It comes from the idea that a clock only strikes up to twelve—so the thirteenth hour is something outrageous, or the moment when a boundary is crossed.
Als er das Auto zerkratzte, schlug es für seinen Vater dreizehn.
When he scratched the car, that was the limit for his father.
three
'drei' and 'dreizehn' are both number words and begin similarly. Even so, 'drei' is the number 3, while 'dreizehn' is the number 13. The risk of confusion comes mainly when listening or reading quickly, because 'dreizehn' starts with 'drei'. Pay attention to the ending '-zehn': it shows that the number is between 10 and 19. With age, dates, prices, or quantities, this difference matters a lot.

Vor dem Wochenende plant die Klasse dreizehn Aufgaben für das Projekt.
Before the weekend, the class plans thirteen tasks for the project.
Das Team schreibt in der E-Mail drei mögliche Termine vor.
In the email, the team suggests three possible appointments.