¹ behind adverb

• in or toward the back
• in the place that someone is going away from —often used figuratively
• later in time

² behind preposition

• in or to a place at the back of or to the rear of (someone or something)
• losing to (someone or something) in a race or competition
• in a less advanced position than (someone or something) : not happening or proceeding as quickly as (someone or something)

³ behind noun

• the part of the body above the legs that is used for sitting : buttocks