What are heteroatoms?

Some articles on heteroatom, heteroatoms:

Heterocyclic Compound - 5-Membered Rings
... Five-membered rings with one heteroatom Heteroatom Saturated Unsaturated Nitrogen Pyrrolidine (Azolidine is not used) Pyrrole (Azole is not used) Oxygen Tetrahydrofuran(Oxolane is rare) Furan (Oxol ... Heteroatom Saturated Unsaturated (and partially unsaturated) Nitrogen/nitrogen Imidazolidine Pyrazolidine Imidazole (Imidazoline) Pyrazole (Pyrazoline) Nitrogen/oxygen Oxazolidine ... Heteroatom Saturated Unsaturated 3 × Nitrogen Triazoles 2 × Nitrogen / 1 × oxygen Furazan Oxadiazole 2 × Nitrogen / 1 × sulfur Thiadiazole 1 × Nitrogen / 2 ...
Skeletal Formula - The Skeleton
... Skeletal atoms other than carbon or hydrogen are called "heteroatoms" ... with a "C"), whereas heteroatoms are always explicitly noted as such (i.e ... using "N" for nitrogen, "O" for oxygen, etc.) Heteroatoms and other groups of atoms that give rise to relatively high rates of chemical reactivity, or introduce specific and interesting ...
Heterocyclic Compound - 6-Membered Rings
... Six-membered rings with a single heteroatom Heteroatom Saturated Unsaturated Nitrogen Piperidine (Azinane is not used) Pyridine (Azine is not used) Oxygen Oxane Pyran (2H-Oxine is not used ...