Answer:
Matter
Compound
Explanation:
Caffeine is NOT an Element, because it is formed by different elements (C, H, N, and O).
Caffeine is NOT an Isotope, because this only applies to elements with the same atomic number but different mass number.
Caffeine is Matter because it has mass and occupies space by having volume.
Caffeine is a Compound because it has a formula with a definite constant composition of different elements.