The roles companion animals have played in our lives has dramatically changed over the last few decades. At the same time, the terms we use to describe both the people and animals in these human-animal relationships have also changed. One example includes the use of the terms 'owner' or 'guardian' to refer to the human caretaker. While preferences by society appear to indicate increased interest in referring to companion animal caretakers as 'guardians', others have cautioned against its use or attempted to restrict it. Additionally, the use of animal welfare terminology has direct implications for how we conduct both welfare research and practice. Our paper examines the use of 'owner' and 'guardian' with respect to (1) the implications for changing terminology on the function, clarity and uniformity of their use, and (2) the ethical and welfare impact that coincides with each term's use. Our goal is to propose terminological considerations that could influence future welfare research, as well as help guide our interactions with companion animals.