1. ratio; proportion
水と砂糖を二対一の比で混ぜる。Mix water and sugar in a ratio of two to one.
2. match; equal; equivalent; comparison
さっきの比じゃない。It's nothing compared to a moment ago.
3. compared with ...; relative to ...
人口比で見ると、この町は医者が多い。Relative to its population, this town has a lot of doctors.
4. Philippines
比政府は新しい政策を発表した。The Philippine government announced a new policy.
5. explicit comparison (style of the Shi Jing)