Structure Isomerism : Important Points
| Isomers | Characteristics | Conditions |
| Chain Isomers | They have different size of main chain or side chain | They have same nature of locants |
| Positional Isomers | They have different position of locants | They should have same size of main chain and side chain and same nature of locant |
| Functional Isomers | Different nature of locant | Chain and positional isomerism is not considered |
| Metamerism | Different nature of alkyl group along a polyvalent functional group | They should have same nature of functional groups chain & positional isomer is ignored |
| Tautomerism | Different position of hydrogen atoms | The two functional isomers remains in dynamic equilibrium to each other |