• The longest continuous chain containing the carbon atoms involved in the multiple bonds is selected.
  
  
• While writing the name of the alkene or alkyne, the suffix 'ane' of the corresponding alkane is replaced by 'ene' or 'yne' respectively.
• If the multiple bond occurs twice in the parent chain, the alkene and alkyne are called diene and diyne respectively.
• The numbering of atoms in parent chain is done in such a way that the carbon atom containing the double or triple bond gets the lowest number.
  Correct
  
  Wrong
  
• All the rules for naming the side chains or substituents are similar to alkanes.

Important Note: If both double and triple bonds are present in a parent chain, the following rules should be remembered.

• The terminal 'e' in the name is dropped when it is followed by the suffix beginning with 'a', 'i', 'o', 'u' or 'y'.
• Numbers as low as possible are given to double bond and triple bond as a set, even though this may at times give –yne a lower number than –ene. However, if a choice is there, preference for lower locants is given to double bond(–ene).
  
  
  
  The name cannot be Pent – 2 – en – 4 – yne because lowest set is 1,3 rather than 2,4.
  Here are some more examples:
  
  
• In case of cyclic alkenes, the position of double bond is always given the number 1.
  
  
  The name of the compound cannot be 2,3 – Dimethyl cyclohex – 1 – ene because of lowest set rule. When we compare the set (1,6) with (2,3), the former is correct because 1 is lower than 2.