Slowed (conditions)

* A slowed creature's Speed is halved. * A slowed creature takes a −2 penalty to AC and Dexterity saving throws. * A slowed creature cannot take reactions. * On its turn, a slowed creature can take either an action or a bonus action, not both. In addition, it can't make more than one melee or ranged attack during its turn.

Source: Adventurer's Guide — official document