Codenames are used to denote the identity of a person, group, or operation that needs to be kept confidential. However, there are a variety of other terms that can be used in place of the term 'codename,' depending on the circumstances. The term pseudonym, for example, refers to a false name or alias that is used to conceal a person's identity. A nickname, on the other hand, is a casual name given to a person or thing that replaces their actual name. A code phrase is a secret term used to convey a message, while an alias can be a fake name adopted by someone to conceal their real identity. Overall, these terms are all used in different contexts to refer to the same concept: a substitute name that conceals the true identity of a person or organization.