Personal space is best defined as:

Personal space is best defined as a body buffer zone between individuals because it refers to the physical and psychological distance that people maintain between themselves and others during interactions. This zone varies depending on cultural contexts, personal preferences, and the nature of the relationship between individuals. Personal space is not just about physical distance but also involves comfort levels and feelings of safety.

While the concept of a physical barrier between friends or a fixed boundary in social settings may involve aspects of personal space, they do not fully encompass the nuanced experience of how individuals perceive and negotiate their comfort levels with others. Similarly, emotional distance between people relates more to psychological and relational dynamics, rather than the immediate physical space between individuals. Hence, understanding personal space as a body buffer zone captures its essence as it is fundamentally about the immediate interactions and spatial dynamics in social contexts.