S — Single Responsibility Principle (SRP)

O — Open/Closed Principle (OCP)

L — Liskov Substitution Principle (LSP)

I — Interface Segregation Principle (ISP)

Clients should not be forced to depend on methods they do not use.

//Bad Example

interface Worker {
void work();
void eat();
}
A robot doesn't eat.

Good Example

interface Workable {
 void work();
}

interface Eatable {
 void eat();
}

Classes implement only the interfaces they need.

D — Dependency Inversion Principle (DIP)