der Nichtraucher
non-smoker
A person who does not smoke, or does not smoke habitually.
Als überzeugter Nichtraucher stört ihn der Zigarettenqualm sehr.
As a committed non-smoker, cigarette smoke bothers him a lot.

non-smoker
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non-smoker
A person who does not smoke, or does not smoke habitually.
Als überzeugter Nichtraucher stört ihn der Zigarettenqualm sehr.
As a committed non-smoker, cigarette smoke bothers him a lot.

The word is made up of the negation prefix 'Nicht-' (non-) and the noun 'Raucher' (smoker). So it literally means a person who is not a smoker.
Mein Vater ist seit zwanzig Jahren Nichtraucher.
My father has been a non-smoker for twenty years.
The context tells you whether a person or an area is meant. If you are talking about a person and their habits, meaning 1 is meant. If it is about places such as trains, restaurants, or hotel rooms, meaning 2 is meant.
Als Nichtraucher fühle ich mich hier unwohl.
As a non-smoker, I feel uncomfortable here.
In the meaning 'Bereich' (area), 'Nichtraucher' (non-smoking) is often the first part of a compound noun. Examples are 'das Nichtraucherabteil' (non-smoking compartment), 'das Nichtraucherzimmer' (non-smoking room), or 'der Nichtraucherbereich' (non-smoking area).
Für unsere Reise buchten wir ein Nichtraucherzimmer im Hotel.
For our trip, we booked a non-smoking room at the hotel.
smoker
'Raucher' and 'Nichtraucher' are clear opposites. A 'Raucher' is a person who smokes regularly; a 'Nichtraucher' does not smoke, or does not smoke habitually. The words can also refer to areas: in the past, for example, there was a 'Raucher' (smoking compartment) and a 'Nichtraucher' (non-smoking section) on trains. Learners may confuse them because they look almost the same. Pay special attention to 'Nicht-': it reverses the meaning.

Simon ist Nichtraucher und wünscht sich ein Hotelzimmer ohne Rauchgeruch.
Simon is a non-smoker and wants a hotel room that does not smell of smoke.
Vor dem Büro stehen einige Raucher, weil sie drinnen nicht rauchen dürfen.
Some smokers are standing outside the office because they are not allowed to smoke inside.