Initial	Acronym	Concept
S	SRP	Single responsibility principle: a class should have only a single responsibility (i.e. only one potential change in the software's specification should be able to affect the specification of the class)
O	OCP	Open/closed principle: “software entities … should be open for extension, but closed for modification.”
L	LSP	Liskov substitution principle: “objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program.” See also design by contract.
I	ISP	Interface segregation principle: “many client-specific interfaces are better than one general-purpose interface.”
D	DIP	Dependency inversion principle: one should “Depend upon Abstractions. Do not depend upon concretions.” Dependency injection is one method of following this principle.

Single responsibility principle

Open/closed principle

Liskov substitution principle

Interface segregation principle

Dependency inversion principle