die Unterhose
underpants
A piece of clothing worn as part of underwear directly on the skin on the lower body.
Er hat sich eine neue Packung Unterhosen gekauft.
He bought himself a new pack of underpants.

underpants
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underpants
A piece of clothing worn as part of underwear directly on the skin on the lower body.
Er hat sich eine neue Packung Unterhosen gekauft.
He bought himself a new pack of underpants.

The word is a clear compound made up of 'unter' (under) and 'Hose' (pants/trousers). It literally describes pants that you wear under your normal clothing.
Kinder lernen oft im Kindergarten, ihre Unterhose selbst anzuziehen.
Children often learn in kindergarten to put on their underpants by themselves.
The prefix 'Unter-' often marks clothing that is worn directly on the skin. 'Die Unterhose' (underpants) belongs together with 'dem Unterhemd' (undershirt) to the broader category 'die Unterwäsche' (underwear).
Für die Reise packte er nur Unterwäsche und ein paar T-Shirts ein.
For the trip, he packed only underwear and a few T-shirts.
In everyday language, 'Unterhose' (underpants) is often used with the verbs 'anziehen' (to put on), 'ausziehen' (to take off), or 'wechseln' (to change).
Nach dem Sport sollte man eine saubere Unterhose anziehen.
After exercising, you should put on a clean pair of underpants.
pants / trousers
'die Hose' and 'die Unterhose' both belong to clothing for the lower body, but they are not the same thing. You normally wear pants visibly over your underwear. Underpants are underwear and are worn directly against the skin. Learners may confuse the words because both contain the word 'Hose'. The important part is 'unter-': it shows that 'die Unterhose' is worn under other clothing. In normal situations, you say 'Hose' when you mean the outer item of clothing.

Nach dem Duschen legt Paul eine frische Unterhose bereit.
After showering, Paul lays out a fresh pair of underpants.
Heute ist ihre Hose zu kurz, weil sie gewachsen ist.
Today her pants are too short because she has grown.