What is the common noun in you will go swimming lake tomorrow?

The common noun in the sentence "You will go swimming in the lake tomorrow" is lake.

Here's why:

* Common noun: A general name for a person, place, or thing.

* Lake: A large body of water surrounded by land.

The other words in the sentence are:

* You: A personal pronoun.

* Will: A helping verb.

* Go: A verb.

* Swimming: A gerund (verb functioning as a noun).

* In: A preposition.

* The: A definite article.

* Tomorrow: An adverb.