Group the following nouns by their part of speech.
dog, book, bird, library
Nouns: dog, book, bird, library

All the nouns in the input belong to the same part of speech. They are all common nouns.
Complete the following task based on the instruction and optional input provided.### Instruction:
Group the following nouns by their part of speech.

### Input:
dog, book, bird, library

### Output:
Nouns: dog, book, bird, library

All the nouns in the input belong to the same part of speech. They are all common nouns.