The word "cost-free" can easily be replaced with several synonymous terms, some of which include "free of charge", "complimentary", "gratis", "at no cost", "for nothing", "chargeless", "without expense", "without payment", "for free", and "for no charge". These synonyms are commonly used when referring to something that is being offered or provided to someone without any financial obligation on their part. It is important to note that while these terms may have slightly different connotations, they all convey the same basic meaning of being able to obtain something without having to pay for it.