# OOP glossary: Freelancer level

20 OOP terms at the Freelancer level, each with a short definition and a link to its full page.

Updated: September 27, 2026

[Study these as flash cards](https://www.ask-codey.com/decks/oop/freelancer)

- [Abstraction](https://www.ask-codey.com/glossary/abstraction): Abstraction is the concept of focussing on only what is needed to solve the current…
- [Adapter Pattern](https://www.ask-codey.com/glossary/adapter-pattern): A pattern that makes one interface look like another, like a travel plug adapter.
- [Builder Pattern](https://www.ask-codey.com/glossary/builder-pattern): A pattern for building a complicated object step by step.
- [Decorator Pattern](https://www.ask-codey.com/glossary/decorator-pattern): A pattern that wraps an object to add behavior without changing its class.
- [Dependency Injection](https://www.ask-codey.com/glossary/dependency-injection): Handing a class the things it needs instead of letting it create them.
- [Dependency Inversion Principle](https://www.ask-codey.com/glossary/dependency-inversion-principle): Depend on interfaces, not on specific implementations.
- [Design Pattern](https://www.ask-codey.com/glossary/design-pattern): A named, proven solution to a common code design problem.
- [DRY Principle](https://www.ask-codey.com/glossary/dry-principle): "Don't Repeat Yourself": keep each piece of knowledge in one place.
- [Factory Pattern](https://www.ask-codey.com/glossary/factory-pattern): A pattern that puts object creation in one place so callers don't pick the class.
- [Interface Segregation Principle](https://www.ask-codey.com/glossary/interface-segregation-principle): Prefer small, focused interfaces so classes only provide what they need.
- [Law of Demeter](https://www.ask-codey.com/glossary/law-of-demeter): A method should talk to its direct collaborators, not reach deep into their parts.
- [Liskov Substitution Principle](https://www.ask-codey.com/glossary/liskov-substitution-principle): A child class must work anywhere its parent class is expected, without surprises.
- [Observer Pattern](https://www.ask-codey.com/glossary/observer-pattern): A pattern where subscribers are notified automatically when something changes.
- [Open/Closed Principle](https://www.ask-codey.com/glossary/open-closed-principle): Add new behavior by adding code, not by changing code that already works.
- [Repository Pattern](https://www.ask-codey.com/glossary/repository-pattern): A pattern that hides data storage behind a simple collection-like interface.
- [Single Responsibility Principle](https://www.ask-codey.com/glossary/single-responsibility-principle): A class should have one job, and so only one reason to change.
- [Singleton Pattern](https://www.ask-codey.com/glossary/singleton-pattern): A pattern that allows only one object of a class for the whole program.
- [SOLID Principles](https://www.ask-codey.com/glossary/solid-principles): Five guidelines for keeping object-oriented code easy to change.
- [Strategy Pattern](https://www.ask-codey.com/glossary/strategy-pattern): A pattern where interchangeable classes each hold one way of doing a task.
- [Tell, Don't Ask](https://www.ask-codey.com/glossary/tell-don-t-ask): Tell an object what to do instead of pulling its data out and deciding for it.

- Previous level: [Journeyman](https://www.ask-codey.com/glossary/subjects/oop/journeyman)
- Next level: [Master](https://www.ask-codey.com/glossary/subjects/oop/master)

[Every OOP term, by level](https://www.ask-codey.com/glossary/subjects/oop)

Source: https://www.ask-codey.com/glossary/subjects/oop/freelancer