Final answer:
Erving Goffman would call the subtle exchange where two people glance at each other on a sidewalk and then look away a 'negligible interaction', reflecting everyday social performances and etiquette.
Step-by-step explanation:
Erving Goffman would refer to the brief and subtle interaction between two people who glance at each other and then look away as they pass by on a sidewalk as a negligible interaction.
This concept is in alignment with his studies about the presentation of self in everyday life and the nuances of social interactions, where every action or lack of it conveys certain meanings within a given context.
Goffman's research explored the subtleties of social conduct, the performances individuals give in everyday interactions, and the unspoken rules they follow to maintain social order and convey impressions to others.
These negligible interactions contribute to the social fabric by allowing individuals to acknowledge each other's presence without demanding further social engagement, thus adhering to a form of social etiquette.