Deny is a mechanic from Dota 2, the reverse of the last hit. If a last hit is finishing off an enemy creep for gold and experience, then a deny is finishing off your own creep, building, or even hero, so that the enemy nearby gains less benefit from it. The word comes from the English "deny" — to refuse, to not allow.
How it works
A creep on your own team can be denied once its health drops below roughly half — that's when attacking it becomes possible. If the deny succeeds, the enemy hero either gets no gold from that creep at all or gets a reduced amount, and receives less experience than they would from a normal creep death. The same applies to towers: a friendly tower that's about to fall is finished off so enemies can't claim the full gold and experience bonus for destroying it.
In critical situations, players even deny heroes — for example, an ally who is dying from enemy spells and is about to grant the opponent gold and experience for the kill. By finishing them off first, the team keeps some of the experience for themselves, while the enemy gets less.
Why it matters
In the early stages of a match, especially during the laning phase, deny is one of the tools of pressure. A player who actively denies creeps deprives their opponent of resources for development, slows their growth, and thereby strengthens their own advantage on the lane. This requires attentiveness: you need to track the health of both your own and enemy creeps simultaneously, and precisely calculate the timing of the attack.
Deny is especially valued by experienced players in the carry and support roles, for whom controlling the lane and preventing the opponent from farming peacefully is crucial. In high-level team games, skillful denying of buildings and creeps at decisive moments of the match can noticeably affect the balance of resources between teams.
In Dota 2, deny is a prominent part of the laning mechanics, one that is absent in many other MOBAs and shooters, which is why the term has become firmly associated with this game and its community.