Any visitor to the school has to be authorized by the school office.
He returned home to find that a visitor had left a note on his door.
The visitor was kindly welcomed.
The visitor wanted to see the sights.
My mother is a frequent visitor to the mall.
In the sentence "your cousin is always a welcome visitor," the word "welcome" is being used as an adjective to describe the type of visitor your cousin is.
A translunar visitor is called an alien.
I am not writing a sentence using that word.
I can give you a sentence using the word galaxy.
This is a sentence using the word aviator.
a sentence using the word endotracheal
Visitor
This is a sentence using the word monomer. :P
I am saying a sentence using the word collagen.