Ability Score: The six fundamental attributes of every character: Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma.

AC (Armor Class): The measure of how hard it is to land a damaging hit on a character or creature.

Advantage: When a player is allowed to roll two d20s and take the higher result, often due to beneficial circumstances.

Alignment: The moral and ethical compass that guides a character's decisions, traditionally defined along the axes of good vs evil and law vs chaos.

AoE (Area of Effect): Spells or abilities that affect a certain area rather than a specific target.

Attack Roll: The roll made to see if an attack hits a target. It is compared against the target's AC.

BBEG (Big Bad Evil Guy): The main antagonist of a campaign.

Buff: A spell or ability that enhances a character's abilities or stats.

Campaign: A series of adventures connected by a common storyline.

Cantrip: A simple spell that can be cast without using up a spell slot.

Charisma (CHA): The ability score representing a character's personality, persuasiveness, and personal magnetism.

Class: The primary occupation or profession of the player character.

Concentration: A requirement for some spells where the caster must maintain focus to keep the spell active.

Constitution (CON): The ability score representing a character's health and stamina.

CR (Challenge Rating): A numerical indication of how tough a creature is in combat.

Crit (Critical Hit): A term used when a player rolls the highest possible result on an attack roll, usually a 20 on a d20 dice.

Critical Failure (Fumble): The result of rolling a 1 on a d20, often resulting in a humorous or dramatic failure.

D20: A twenty-sided die, the most commonly used die in D&D.

DC (Difficulty Class): The target number that a player must meet or exceed in order to succeed at a task.

Debuff: A spell or effect that negatively impacts a character's abilities or stats.

Dexterity (DEX): The ability score representing a character's agility, reflexes, and balance.

DM (Dungeon Master): The person who runs the game, controls NPCs, and narrates the story.

DMPC (Dungeon Master Player Character): A character controlled by the DM that acts as a regular member of the party.

DPS (Damage per Second): A term borrowed from video games that refers to how much damage a character can deal in a given amount of time.

DR (Damage Resistance): A type of special defence that reduces damage from certain types of attacks.

Dungeon: A game environment, often filled with monsters and treasure.

Encounter: A specific event or situation in the game, often a combat situation.

Experience Points (XP): Points gained from overcoming challenges or completing quests that help characters level up.

Familiar: A magical creature that serves a spellcaster, often providing various benefits.

Feats: A special capability that gives a character unique abilities or improves existing ones.

Fumble: See Critical Failure.

GM (Game Master): Another term for a Dungeon Master, more common in other RPGs.

Grapple: A special melee attack that involves seizing a target to restrict its movement.

HP (Hit Points): The measure of how much damage a character can take before falling unconscious or dying.

Initiative: A roll at the start of combat to determine the order in which characters act.

Intelligence (INT): The ability score representing a character's mental acuity, information recall, and analytical skill.

Ki: A resource used by monks in D&D to fuel their special abilities.

Lawful, Chaotic, Neutral, Good, Evil: The five possible components of a character's alignment, defining their moral and ethical outlook. See Alignment

Level: The measure of a character's overall power and skill.

Long Rest: A period of extended downtime, usually 8 hours, during which characters recover hit points and other resources.

Loot: The treasure and rewards gained from adventuring.

Melee: Close-quarters combat, as opposed to ranged combat.

Metagaming: Using out-of-game knowledge in the game world, often discouraged as it can disrupt immersion.

Min-Maxing: The practice of optimizing a character's abilities to the maximum extent possible, often at the expense of roleplaying or story considerations.

Multi-classing: The practice of advancing in more than one class, gaining the benefits of each.

NPC (Non-Player Character): Any character in the game world that is not controlled by a player.

Party: The group of player characters.

Passive Perception: A measure of a character's awareness of their surroundings when not actively looking for something.

PC (Player Character): The character that a player controls in the game.

Proficiency Bonus: A bonus added to rolls for skills and abilities in which a character is proficient.

PvE (Player versus Environment): A term that refers to combat or interaction between the players and the game world, controlled by the DM.

PvP (Player versus Player): A term that refers to combat or interaction between player characters.

Ranged: Combat from a distance, typically using weapons like bows or spells.

RAW (Rules As Written): The literal interpretation of the game rules, as opposed to the spirit or intent of the rules.

Rogue: A class in D&D known for their stealth and agility.

Roll: To throw a die or dice to determine the outcome of an action.

Round: A unit of time in combat, during which each character has a chance to act.

Saving Throw: A roll made to resist or avoid an effect or spell.

Short Rest: A period of brief downtime, usually 1 hour, during which characters can recover a limited amount of resources.

Skill Check: A roll made to determine the outcome of a character using a particular skill.

Spellcasting: The act of using magical spells.

Spell Slot: The resource used to cast spells. Higher-level spells require higher-level slots.

Strength (STR): The ability score representing a character's physical power.

TPK (Total Party Kill): A term used when the entire group of player characters are killed in an encounter.

Turn: A portion of a round in which one character gets to act.

Wisdom (WIS): The ability score representing a character's intuition and common sense.

Saving Throw: A roll made to resist a spell or effect.

Sorcerer: A spellcasting class in D&D that derives its power from a magical bloodline or other inherent magical source.

Spell Level: The relative power of a spell, with higher-level spells being more potent.

Spell Save DC: The Difficulty Class that a target must meet or exceed on a saving throw to avoid or reduce a spell's effects.

Spellbook: A book where wizards record their spells.

Stealth: A skill used to move silently and avoid detection.

Summon: To call forth a creature or entity, usually through magic.

Tank: A character built to absorb damage and protect weaker party members.

Turn Undead: A class feature of clerics, allowing them to repel undead creatures.

Two-Weapon Fighting: A style of combat where a character fights with a weapon in each hand.

Unconscious: A condition in which a character is incapacitated, often due to dropping to 0 hit points.

Underdark: A vast network of subterranean caverns and tunnels in the D&D world, home to many strange and dangerous creatures.

Vancian Magic: The system of magic used in D&D, named after fantasy author Jack Vance, where spellcasters prepare a certain number of spells each day.

Versatile: A property of weapons that can be used with one or two hands, dealing more damage when used with two hands.

Warlock: A spellcasting class in D&D that derives its power from a pact with an otherworldly entity.

Wizard: A spellcasting class in D&D that learns and prepares spells from a spellbook.

XP (Experience Points): Points earned by characters for overcoming challenges and completing tasks or quests. These points are used to level up, gaining new abilities and increasing power.

1d4, 1d6, 1d8, etc.: The notation for rolling dice in D&D. 1d6 means to roll one six-sided die, 1d8 means to roll one eight-sided die, and so forth.

2e, 3e, 4e, 5e: Shorthand for Second Edition, Third Edition, Fourth Edition, and Fifth Edition of D&D, respectively.

20-Sider: Slang term for a d20, the most commonly used dice in D&D.

3d6: The traditional method of generating ability scores, by rolling three six-sided dice and adding them together.

4d6 Drop Lowest: A common method of generating ability scores, by rolling four six-sided dice, removing the lowest roll, and adding the remaining three together.

5-Foot Step: A term from earlier editions of D&D, referring to a small movement that doesn't provoke attacks of opportunity. In 5e, this is replaced by the Disengage action.

5e (Fifth Edition): The latest version of D&D rules, as of my knowledge cutoff in 2021.

6-Second Round: A term referring to the length of a round of combat in D&D, according to the rules.

8-Hour Rest: Refers to the long rest period in D&D during which characters regain hit points and spell slots.

10-foot pole: A classic piece of adventuring equipment often used to check for traps or pitfalls.

1d10: A ten-sided die, often used for certain types of damage or class abilities.

1d100: A percentile roll, typically made with two ten-sided dice of different colors. One represents the tens place and the other the ones place.

12d6: The damage often dealt by very potent spells, like the wizard's fireball spell at high levels.

1st Level, 2nd Level, etc.: Terms used to denote the power and complexity of spells, as well as the progression of player characters.

2-Weapon Fighting: A combat style where a character fights with a weapon in each hand.

24-Hour Rest: A full day of rest in D&D, often used to recover from major wounds or afflictions.

3-Pillar Experience: An optional rule in D&D 5e where experience points are awarded for exploration and social interaction, in addition to combat.