Berzelius is credited with originating the chemical terms "catalysis", "polymer," "isomer," "protein" and "allotrope," although his original definitions in some cases differ significantly from modern usage. As an example, he coined the term "polymer" in 1833 to describe organic compounds which shared identical empirical formulas but which differed in overall molecular weight, the larger of the compounds being described as "polymers" of the smallest. At this time the concept of chemical structure had not yet been developed so that he considered only the numbers of atoms of each element. In this way, he viewed for example glucose (CHO) as a polymer of formaldehyde (CHO), even though we now know that glucose is not a polymer of the monomer formaldehyde.