pentoxide

As a noun pentoxide

is .

As an adjective undefined is

lacking a definition or value.

In chemistry terms the difference between phosphorus and pentoxide

is that phosphorus is a chemical element (symbol P) with an atomic number of 15, that exists in several allotropic forms while pentoxide is any oxide containing five oxygen atoms in each molecule.

As a proper noun Phosphorus

is a name sometimes used for Hesperus, the personification in Greek mythology of the planet Venus.

In chemistry terms the difference between pentoxide and pentoxide

is that pentoxide is any oxide containing five oxygen atoms in each molecule while pentoxide is any oxide containing five oxygen atoms in each molecule.