You Aren't Gonna Need it (YAGNI)
You Aren't Gonna Need it (YAGNI) is a mnemonic to help limit scope in requirements. YAGNI advises that there's no point in building capabilities into products until there is an observable need. Though applicable to virtually any engineering project, YAGNI is especially applicable to software because it's so easy to change compared to other types of engineering projects.
Broader Topics Related to You Aren't Gonna Need it (YAGNI)
Resources for Project Management
Elements of well-formed requirements: The fundamental building blocks of product engineering