On what two grounds is it customary to classify organic substances?

Classification of organic substances:
1) in terms of the number, position and nature of functional groups – aldehydes RCHO, carboxylic acids RCOOH, alcohols ROH, etc.

2) on the carbon skeleton:
a) acyclic (aliphatic)
i) limiting CH3-CH2-CH3
ii) unsaturated CH3-CH = CH2

b) cyclic
i) alicyclic
– carbocyclic (contain a cycle of only carbon atoms (cyclopentane, cyclohexane))
– heterocyclic (in the cycle, in addition to carbon atoms, there are atoms of other elements (pyrrolidine, tetrahydrofuran)
ii) aromatic
– carboaromatic (benzene, toluene)
– heterocyclic (heteroaromatic) (pyridine, thiophene, furan)