an act of copying
"The teacher caught him in the act of copying her notes without permission."
an instance of the making of a copy
"The librarian noticed that copying his rare book was damaging its fragile pages."
In plain English: Copying is when you make an exact duplicate of something, like taking notes from someone else's homework without doing your own work.
"The teacher warned the class that copying other students' homework would result in failing the assignment."
present participle of copy
"The students were caught copying each other's homework during the test."
In plain English: Copying is making an exact duplicate of something by repeating it exactly as you see it.
"She was caught copying her neighbor's homework during class."