What differentiates a friend from an acquaintance? When does one become the other?
An acquaintance is somebody you are friendly with but not fully comfortable with. A friend is somebody you can sit in silence with and not think it awkward. An acquaintance is somebody you censor yourself around. A friend is somebody you can be yourself around, and not worry about being judged. Even if your friend disagrees with you, a friend respects your difference of opinion.