Ratio Decidendi (Reason for the Decision):

This is the main reason behind a court’s decision. It is the key legal principle or rule that forms the basis of the judgment. The Ratio Decidendi becomes binding for similar future cases.

• Example:
  In the case of Kesavananda Bharati v. State of Kerala (1973), the court ruled that the basic structure of the Constitution cannot be amended. This reasoning is the Ratio Decidendi and must be followed in later cases involving constitutional amendments.

2. Obiter Dictum (Said in Passing):

These are comments or opinions made by a judge while giving a judgment that are not directly related to the decision of the case. They are not binding on future cases.

• Example:
  In IC Golak Nath v. State of Punjab (1967), the court observed that Parliament should not amend Fundamental Rights, but this was not the main decision of the case. It was an obiter dictum and therefore not binding in later cases.

3. Per Incuriam (Through Lack of Care):

This happens when a court makes a decision without properly considering a law or a legal precedent that should have been followed. Such decisions are considered mistakes and are not binding.

• Example:
  In State of Orissa v. Nalinikanta Muduli (1963), the court ignored a prior legal provision, leading to a per incuriam decision. This mistake was later corrected by other judgments.

4. Sub Silentio (Under Silence):

This means a court decision is made without addressing a particular legal issue or argument that was relevant to the case. Such decisions do not hold strong authority because the issue was not discussed properly.

• Example:
  In A-G v. Ryan (1980), the court ruled on a case but skipped discussing an important statutory provision. This made the decision sub silentio and less authoritative for similar future cases.