Which document serves as proof of identification and national origin when traveling?

A passport serves as a crucial document for international travel as it not only functions as proof of identity but also establishes a traveler’s nationality. This means it provides verification of a person’s nationality, thereby allowing them to enter other countries or return to their home country. Unlike a driver's license or a national ID card, which primarily demonstrate identity and may or may not indicate nationality, a passport is specifically designed for global travel and is recognized internationally as a standard form of identification. Additionally, a certificate of citizenship serves as proof of citizenship status but is not typically used for identifying oneself in travel situations. Thus, the passport is the most comprehensive document listed for demonstrating both identification and national origin when traveling.