Speed

Speed is a monster property in NetHack, also referred to internally as movement rate. For every turn that passes a monster will gain its movement rate in "movement points"; if the monster has 12 or more movement points (defined as NORMAL_SPEED ) in a turn it gets a move that turn (and more than one if it has another 12 points remaning after this, etc.) Thus a monster with a speed of 12 gets one move per turn, a monster with a speed of 1 gets one move every 12 turns, and a monster with a speed of 18 gets 3 moves every 2 turns.

A very fast player (obtained through speed boots or a potion of speed) grants an extra guaranteed extra six movement points per turn, and one turn out of three another extra six movement points, thus having the player move with an effective movement rate of 20, or five thirds normal, giving five moves every three turns. A fast player (obtained through wands of speed monster, quantum mechanic corpses, etc.) grants six movement points two turns out of three, resulting in an effective movement rate of 16, or four thirds normal, giving four moves every three turns.

A monster with intrinsic speed (gained by e.g. a wand of speed monster) has four thirds their normal movement rate ; a slowed monster (by means of a wand of slow monster) has two thirds their normal movement rate.

Being encumbered reduces the player's effective movement speed after speed adjustments. A burdened player has three quarters their normal movement rate, a stressed player one half, a strained player one quarter, and an overtaxed player one eighth.