A delegate is a type-safe method reference. It can be used to execute any method with a matching signature.

An event is a field that is a delegate having the event keyword applied. The keyword ensures that only += and -= are used; this safely combines multiple delegates without replacing any existing event handlers.

A derived class (or subclass) is a class that inherits from a base class (or superclass).

The is operator returns true if an object can be cast to the type. The as operator returns a reference if an object can be cast to the type; otherwise, it returns null.

Find more information on the sealed keyword at https://msdn.microsoft.com/en-us/library/88c54tsw.aspx

Find more information on the abstract keyword at https://msdn.microsoft.com/en-us/library/sf985hc5.aspx

Find more information on the virtual keyword at https://msdn.microsoft.com/en-us/library/9fkccyh4.aspx

A destructor, also known as a finalizer, must be used to release resources owned by the object. A deconstructor is a new feature of C# 7 that allows a complex object to be broken down into smaller parts.

The following are the signatures of the constructors that all exceptions should have:

An extension method is a compiler trick that makes a static method of a static class appear to be one of the members of a type. You define which type you want to extend by prefixing the type with this.