POLYMERS
A polymer is any of a class of natural or synthetic substances composed of very large molecules, called macromolecules, which are multiples of simpler chemical units called monomers.
CHEMICALS
A chemical is any substance that has a defined composition. In other words, a chemical is always made up of the same "stuff".
FERTILIZERS
Fertilizers are organic or inorganic substances containing chemical elements that improve the growth of plants and the fertility of the soil.