An easy way to experience alienation from your nice-smelling friends is to go a month without bathing. Alienation is a state of being cut off or separate from a person or group of people.
The noun alienation describes the feeling that you're not part of a group. Your political views might cause you to feel a sense of alienation from the rest of your family, or your vegetarianism could result in alienation from your meat-eating friends. The Latin word for alien is alienus, "belonging to another." That idea of not belonging, or not fitting in, gave rise to the Latin verb alienare, "to estrange," which alienation comes from.