Do All common nouns begin with a capital letter?

No, common nouns do not begin with a capital letter unless they are at the beginning of a sentence or part of a proper noun.

Here's why:

* Common nouns are general names for people, places, or things. They are not specific and can be used for many different individuals or objects. Examples include:

* dog

* city

* book

* river

* Proper nouns are specific names for people, places, or things. They are always capitalized. Examples include:

* Fido (a specific dog)

* London (a specific city)

* The Lord of the Rings (a specific book)

* Mississippi River (a specific river)

In summary: Common nouns are generally lowercase, while proper nouns are capitalized.