der Teenie
teen
A colloquial term for a teenager, that is, a person between the ages of 13 and 19.
Als Teenie habe ich stundenlang mit meinen Freunden telefoniert.
As a teen, I spent hours talking on the phone with my friends.

teen
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teen
A colloquial term for a teenager, that is, a person between the ages of 13 and 19.
Als Teenie habe ich stundenlang mit meinen Freunden telefoniert.
As a teen, I spent hours talking on the phone with my friends.

'Teenie' (teen) is a colloquial short form derived directly from the English word 'teenager'. The ending '-ie' is often used in German for such diminutive or informal forms from English.
Viele Teenies interessieren sich für die neueste Mode und Musik.
Many teens are interested in the latest fashion and music.
'Teenie' (teen) is often used as the first part of compound words to describe things that are typical for this age group. Examples include music, idols, or problems.
Die Band war in den 90ern ein gefeiertes Teenie-Idol.
The band was a celebrated teen idol in the 90s.
The word 'Teenie' (teen) clearly belongs to colloquial language. It is used almost exclusively in spoken language or in informal texts such as magazines and blogs.
Meine Tochter ist jetzt ein Teenie und hat ihren eigenen Kopf.
My daughter is a teen now and has a mind of her own.
adult
'der Erwachsene' and 'der Teenie' both refer to people, but they are clearly opposite in terms of age. An adult is no longer a child or teenager and is considered of legal age or mature. A 'Teenie' is a colloquial term for a person between 13 and 19 years old. 'Teenie' sounds more informal and fits better in everyday language, while 'Erwachsener' is more neutral and also works well in official situations.

Zu Hause spricht der Teenie beim Frühstück oft über Musik und Schule.
At home, the teen often talks about music and school at breakfast.
Bei der Anmeldung muss ein Erwachsener unterschreiben.
An adult must sign the registration form.