Reach
A creature has a reach of 5 feet unless a rule says otherwise.
Reaction
A Reaction is a special action taken in response to a trigger defined in the Reaction’s description. You can take a Reaction on another creature’s turn, and if you take it on your turn, you can do so even if you also take an action, a Bonus Action, or both. Once you take a Reaction, you can’t take another one until the start of your next turn. The Opportunity Attack is a Reaction available to all creatures. See also “Opportunity Attacks” and “Playing the Game” (“Actions”).
Ready [Action]
You take the Ready action to wait for a particular circumstance before you act. To do so, you take this action on your turn, which lets you act by taking a Reaction before the start of your next turn. First, you decide what perceivable circumstance will trigger your Reaction. Then, you choose the action you will take in response to that trigger, or
Resistance
If you have Resistance to a damage type, damage of that type is halved against you (round down). Resistance is applied only once to an instance of damage. See also “Playing the Game” (“Damage and Healing”).
Restrained [Condition]
While you have the Restrained condition, you experience the following effects. Speed 0. Your Speed is 0 and can’t increase. Attacks Affected. Attack rolls against you have Advantage, and your attack rolls have Disadvantage. Saving Throws Affected. You have Disadvantage on Dexterity saving throws.
Ritual
If you have a spell prepared that has the Ritual tag, you can cast that spell as a Ritual. The Ritual version of a spell takes 10 minutes longer to cast than normal. It also doesn’t expend a spell slot, which means the ritual version of a spell can’t be cast at a higher level. See also “Spells.”
Round Down
Whenever you divide or multiply a number in the game, round down if you end up with a fraction, even if the fraction is one-half or greater. Some rules make an exception and tell you to round up.