Why are appositive phrases set off by commas?

Can an infinitive be the subject of a sentence?

What famous line in Hamlet repeats the same infinitive twice?

True or false: An infinitive can sometimes act as a noun.

Is "sadness" a concrete noun?

True or false: "Pumpkins" is a countable noun.

True or false: "Freshness" is a collective noun.

True or false: "Flock" is a collective noun.

True or false: "Wine" is a non-countable (mass) noun.

Is "rain" a countable noun?

True or false: "Rims" is a countable noun.

True or false: "Air" is a countable noun.

True or false: All proper nouns are capitalized.

True or false: "Kleenex" and "Xerox" are the same type of noun.

Are "Skippy" and "peanut" the same type of noun?

What is the difference between a proper noun and a common noun?

True or false: nouns can appear anywhere in a sentence.

What is a common noun?

What is a proper noun?

What is an appositive phrase?

What is an appositive?