Dungeon Crawl is a turn-based game. Every action your character takes progresses the turn counter forward by one, and the game is paused between each of your actions. However, new players quickly observe that character and monster behavior can't simply be measured in turns.
Every character action has an associated delay, measured in aut (arbitrary units of time). Your delay determines how much time passes during a given turn for monsters to take their own actions. Monsters that do not act during a turn are still accumulating time for their next action.
The standard time required for a single turn is 10 auts, or one decaAut. The time that actions actually take is dependent on what type of action, but other factors like haste, slow, or weapon skill may change them. However, most species and monsters move at 1 decaAut, and it is the normal time it takes to consume an item.
A well-equipped, high level character can sometimes attack for multiple turns in the time it takes a monster to act once, but this depends on the particular monster you face. Although most creatures are designed to act about as often as an average character, many are significantly faster or slower than you; some creatures may even move and attack at different speeds!
"Delay" vs "Speed"
Speed, which is used for monster stats, is not the same as delay. A 10 speed monster takes 1 decaAut to move, but a 5 speed monster takes 10/5 = 2 decaAut, while a 20 speed monster takes 10/20 = 0.5 decaAut to move. The game doesn't track time past single aut; instead, monsters with a decimal delay will be rounded up or down in a weighted fashion. A monster with a calculated 0.54 decaAut (5.4 aut) delay has a 40% chance to take 5 aut and a 60% chance to take 6 aut for their action. The same rounding applies to any other non-granular delay, such as your own weapon speed. Note that monsters and monsters alone are subject to energy randomisation, making their movements less predictable.