What is the meaning of a readonly argument in an interface in Typescript?

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A readonly argument in an interface in Typescript means that the property or field defined in the interface cannot be modified outside the object's constructor. Readonly properties allow for immutability, which can be helpful in writing safer and more concise code. It prevents accidental changes to important properties, which can lead to unexpected behavior. Once assigned in the constructor, the readonly property cannot be modified or overwritten.