covering

a natural object that covers or envelops; "under a covering of dust"; "the fox was flushed from its cover"

an artifact that covers something else (usually to protect or shelter or conceal it)

the act of concealing the existence of something by obstructing the view of it; "the cover concealed their guns from enemy aircraft"

the act of protecting something by covering it

the work of applying something; "the doctor prescribed a topical application of iodine"; "a complete bleach requires several applications"; "the surface was ready for a coating of paint";