¹ before adverb

• at an earlier time
• to or toward the place where someone is going : in advance

² before preposition

• at a time preceding (something or someone) : earlier than (something or someone)
• —used to describe a time earlier than a specified hour
• preceding (something or someone) in order or in a series

³ before conjunction

• earlier than the time that : earlier than when
• until the time that
• —used to refer to something that might happen