The primary difference between "domo" and "domo arigato" lies in their level of explicitness, completeness, and social register. "Domo" is an extremely casual, versatile shorthand expression that functions like saying "thanks" or offering a breezy nod of acknowledgment. It is short, open-ended, and relies entirely on context to convey gratitude or greeting. In contrast, "domo arigato" explicitly includes the root word for thank you (arigato), making the expression of appreciation much more direct and unmistakable. Despite containing arigato, "domo arigato" is still considered moderately casual in native Japanese conversation because it lacks the final polite suffix gozaimasu. While pop culture often portrays "domo arigato" as a standard polite phrase, native speakers in formal or business settings almost always add gozaimasu to create the complete, respectful phrase arigato gozaimasu, reserving "domo" and "domo arigato" for relaxed, everyday interactions among peers.