Damage

Damage represents injury from attacks or natural causes. Players and mobs in Minecraft each have a supply of health points, which are reduced when they are injured. The player has 20 health points, but these are measured on a health gauge with 10 hearts. Thus each health point is "½ a heart", shown as. Mobs have varying numbers of health points, but these are not generally visible to players. However, when riding a tame horse/donkey/mule, the player can see their mount's health, and a dog's health is visible in its tail angle.

Damage from attacks or natural causes will subtract from a player or mob's current health. When their health reaches zero, they die. Players can also recover health naturally by being well-fed, or through magical effects. Most mobs do not recover health except through magic, but horses and dogs can be healed by feeding them.

Armor will absorb some of the damage that would have been done to its wearer, but will take damage itself (to durability) in the process.

Dealing damage
Players can deal damage by hitting mobs or other players with items at close (melee) range. An "unarmed" attack only does damage, but weapons and certain tools do more:
 * Swords are crafted for this purpose. While swords do not extend attack range, they deal significantly more damage than with any other item or tool.
 * Axes, pickaxes, and shovels also deal more damage than bare fists.
 * Any other item is equivalent to fists and does the same damage. This includes hoes, and hitting something directly with a bow or held arrow.
 * While falling, melee attacks deal a critical hit (up to 50% + additional damage, rounded down to the nearest hit point).

There are a few ranged weapons in the game:
 * Arrows are shot by holding and releasing right click when wielding a Bow, and do damage depend on the "charge" of the bow (see below).
 * Snowballs, only inflict damage on Blazes and the Ender Dragon, while chicken eggs damage only the Ender Dragon. Both still knock mobs back as if they had been damaged.
 * Splash potions can be thrown, inflicting various effects depending on the potion.
 * Ender pearls deal damage to only the ender dragon

A few items can be used to damage monsters indirectly:
 * The Flint and steel allows the player to light a block on fire, which causes all players and mobs that touch the fire to be set on fire (some monsters are fireproof, mostly those native to the Nether). Players and mobs that are ignited stay alight until  hit points of damage is dealt, until they touch water, or use a fire resistance potion.
 * Likewise, contact with Lava also ignites players and mobs.
 * TNT is currently the only controllable explosive in Minecraft, and can be triggered by fire, redstone currents, or another explosion.

The below values detail the damage dealt per hit using various items. Critical hits can do variable extra damage.

Anvil
A falling anvil deals serious damage. If it falls from high enough, it can instantly kill you.

Thorns Enchantment
When a player or mob deals melee or projectile damage to a player or mob that is wearing Thorns-enchanted armor, the attacker will also be damaged.The amount changes with the enchant level.

Suffocation
Suffocation happens when a player or a mob is unable to breathe because its upper half is inside of a block. They will lose every half-second (10 ticks). Due to sand and gravel falling, it can easily cover the player. In first person mode, the player's screen will be blackened when suffering from this condition thus disabling them to see what is happening. In third person mode, the view will automatically switch to first person mode.

When inside a block, the player can easily step out of it as the blocks do not prevent their movement.

The usual ways to get one's head inside a block are:


 * Sand or Gravel falling into the space the player or mob occupies.
 * Riding a Pig, Boat or Minecart or throwing an Ender Pearl into a one-block-high space.
 * Riding a Horse into a two-block-high space.
 * Standing where a tree just grew from a sapling.
 * Standing where a huge mushroom just grew from a mushroom.
 * Standing where an Exit Portal just spawned after killing an Ender Dragon.
 * Having a solid block pushed into your head with a Piston.
 * Sleeping in a bed that is surrounded by blocks and/or has a solid block above it.
 * Being teleported into a block via command blocks or console commands.
 * When playing on a distant server, sometimes broken blocks can reappear because of lag, and if the player moves where the block respawned, it can provoke suffocation (for example, chopping down a tree by moving right below the trunk).

It's worth noting that the player will not suffocate in glass, or indeed in any transparent block. Leaves from a grown Sapling will not suffocate you, even if you're on Fast graphics (which makes leaves appear solid).

Starvation
When the food bar reaches zero, the player will take damage every four seconds. It also shakes indicating you are hungry. The player stops taking starvation damage when the player eats or the health bar drops to health on easy mode or  health on normal mode. In hard mode or hardcore mode, the damage will not stop until the player either dies, or eats something.

Cactus contact
Touching a cactus will cause a player or mob to take damage, and rapidly continue taking damage if they continue to stand on or next to it.

Lava
By far the most dangerous natural occurrence (except for the unlikely case of a player falling into the void), players and mobs will take damage from contact with Lava extremely fast or half second, ( per hit), and stay on fire even if they exit it ( point per hit for 15 hits or more ( total damage) or until extinguished with water). If players do not have a water source available, they will die quickly.

While mining, consider keeping at least one placeable solid block ready somewhere on your toolbar (such as Dirt or Cobblestone) for quick access using your mouse wheel. If you mine into a lava pool, you may be able to place the block in the hole and so prevent burning. It is possible to keep a fire-resistance potion at all times so you can prevent from dying in lava, because if you fall in the lava and act fast enough, you will be able to use the potion in time. If you're not fast enough, or have not enough health to resist the damage while drinking the potion, try using a splash potion of fire-resistance. Or just use a bucket of water (although this doesn't help you in the nether).

Poison
Cave Spiders will poison players when they bite (only in normal and hard difficulty). Eating a Spider Eye, Poisonous Potato, or pufferfish or drinking/being hit by a potion of poison (maybe from witches) will give the same result. While poisoned, the hearts in the health meter turn from red to an olive green and the player takes  each 25 ticks (1.25 seconds) until the poison wears off. The poison itself cannot kill the player, but it can reduce them to 1 hit point, thus leaving them very vulnerable to damage from other sources. Poison can be cured by drinking milk from a bucket.

Wither Effect
Wither and Wither Skeletons will give you the Wither Status effect with their attacks. (The Wither boss's skulls do not inflict the effect on Easy difficulty.) This will darken your health bar to, while inflicting damage over time. The effect deals every 2 seconds (40 ticks) for the Wither Skeleton's attack (level I), and every second (20 ticks) for the Wither boss's skulls. Unlike poison, withering can kill you directly, and the darkened healthbar makes it harder to keep track of the damage.

The Void
If one were to break through the bedrock barrier found at the bottom of worlds, the Void can be seen. Players in the Void, below height -64 will take damage at a rate of about per half-second or  per second. You will usually die from falling in the Void, even in Creative mode, but the player may be saved by throwing an Ender Pearl before they fall to height -64.

Falling into the void in The End is more likely, so players must be cautious when entering The End.

By effecting yourself with resistance 5+ and/or regeneration 8+ you can fall infinitely into the void without dying.

Trivia

 * Critical hits can be done while reflecting a Ghast's fireball, but won't change the damage or speed of it.
 * In Creative mode, attacking a mob while flying after having descended will score a critical hit.
 * When attacking something with a Melee object (Fists, Swords, etc.), there is a brief cooldown before it can be hurt again. Having a Regeneration IV (4) Potion Effect however, seems to remove the cooldown, as the Player/Mob can be hit more often.
 * When a player dies, the player has the same falling-over death animation as all other mobs. This can be seen by being in third-person mode upon death, having your inventory open upon death, or (as of 1.6) witnessing the death of another player in multiplayer.