The biggest difference I've seen in my career: - OOP code is usually separated and organized by the principal data it operates on, i.e. the instance of a class

The biggest difference I've seen in my career: - OOP code is usually separated and organized by the principal data it operates on, i.e. the instance of a class, and more specifically the instance's fields. - FP code is usually separated and organized by the more abstract or philosophical responsibility of the functions, and they may not always share the same arguments.