Some nouns use the same form for both singular and plural. Here are the most common nouns that stay the same when being used as a plural: fish, shrimp, sheep, elk, deer, reindeer, moose, scissors
I saw a deer in my back yard.
I saw two deer in my back yard.
Be aware that certain nouns do not change form when being used as a plural.
It’s your turn. Which word in this sentence stays the same for both singular and plural? We visited a nature park and saw elk, peacocks, and cougars. Did you figure it out? Good for you!