Which word is defined as a person's face or facial expression?

The term 'countenance' specifically refers to a person's face or facial expression, emphasizing the overall appearance and demeanor that can be conveyed through facial features. It encapsulates not only the physical structure of the face but also conveys emotional responses and attitudes, which can be crucial in understanding human interaction.

While 'visage' could also relate to someone's face and is often used in a similar context, it tends to place more emphasis on the physical aspect rather than the expression or the emotional implication. The words 'appearance' and 'expression' provide broader meanings, with 'appearance' being more general and 'expression' focusing solely on conveyed emotions without encompassing the broader essence of the face. Therefore, 'countenance' is the most appropriate choice as it aligns specifically with the concept of facial expression and overall communicative presence.