• 以上いじょう — more than / above
• 以外いがい — except for
• 以来いらい — since
• 以下いか — less than / below
• 以前いぜん — before
• 所以ゆえん — for that reason

以 originally showed a pictograph of a person (人) followed by another symbol suggesting motion or action. It often expresses direction, means, or cause in compound words, and is common in formal language or writing.

それ以外いがいは 全すべて完了かんりょうしました。
Everything except that has been completed.

それは 以前いぜんに 聞ききました。
I heard that before.

彼かれは 以来いらいずっと来こない。
He hasn’t come since then.