P4: -S endings on Nouns: Use -s endings on nouns to show plurals, generality, or to ensure subject-verb agreement. Apostrophe -s is used for possession only. See the following: https://www.gallaudet.edu/tutorial-and-instructional-programs/english-center/grammar-and-vocabulary/five-ways-to-use-s-at-the-end-of-a-noun-or-verb
Put an -s at the end of plural nouns.
Many scientist have been searching for the cure. – Incorrect
Many scientists have been searching for the cure. — Correct
That was a day that most student were not on campus. – Incorrect
That was a day that most students were not on campus. — Correct
Use plural -s endings to express generality.
Mural is what makes the old buildings downtown come alive. – Incorrect
Murals are what make the old buildings downtown come alive. – Correct