nostrils
In German, the word for nostrils is "Nasenlöcher". It is a compound noun, with "Nase" meaning nose and "Löcher" meaning holes. It is used to refer to the two openings in the nose through which air is inhaled and exhaled. It is important to note that, unlike in English, the plural form is used to refer to both openings together.
She has large nostrils.
The sentence describes the physical characteristic of someone, pointing out that the person, a woman in this case, has large nostrils.
He could not breathe well through his nostrils.
This sentence explains a difficulty someone is having physically. Specifically, this person, a man in this instance, is having trouble breathing through his nostrils.
A dog's nostrils are very sensitive.
This sentence refers to a well-known fact about the sensory perception of dogs. It points out the extraordinary sensitivity of a dog's nostrils.