Molecules, names

In the nomenclature of moleculers, we often use prefixes: mono, di, tri, etc.

Example: N2O4 is called: di nitrogen tetra oxyde.
The use of prefixes is limited to those situation where confusion can occur if the prefix is left out.

prefixes you should know:

mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca

"carbon oxyde" is not enough as name, because there are two of them: CO and CO2
CO is called carbon mon(o)oxyde and the other is carbon dioxyde. The o in brackets mostly is left out.
Molecules of an element with Hydrogen often get a traditional name like ammonia, water, natural gas, and more.

In the organic chemistry (carbon chemistry) thereis a very extended system with prefixes.

Meta, eta, propa, buta and then further as known already: penta, hexa, nona, deca etc.
More about this further on.

After all this: there are salts, that, included in an ionic lattice, contain water molecules. But they remain solids! They contain water molecules and we call them: hydrates.

example: Copper(II)sulphate pentahydrate; and another example: Na2CO3.10H2O.