Senpai: Used to refer to a senior member of an organization. In this context, it refers to you.
Servant: Units that you summon from battle, usually spirits based from myth and legends.
Noble Phantasm (NP): Special moves Servants can use when their NP gauge are fully charged.
Spirit Origin: Cards
Craft Essence (CE): Servant Equipment
Mystic Code: Master Equipment
Chaldea Gate: Mission Hub
Singularity: Story Chapter
Holy Grail: Story MacGuffin. Also a very limited resource for raising Servant level cap.
Spirit Origin: List of all seen and acquired Servants
Saint Quartz: Currency used for summoning 3* to 5* cards.
Friend Points: Currency used for summoning 1* to 3* cards.
Mana Prism: Shop Currency
Burning: Selling cards for mana prisms.
QP: Common currency used in leveling and upgrading Servants and Servant skills.
Ascension: Upgrading a Servant; increase level cap and unlocks new skills/portraits/dialogues.
Palingenesis: Upgrading a Servant with a Holy Grail; Also increases max level cap.
Ember/Fire/Blaze of Wisdom: Experience cards used to level up Servants.
Waifu / Husbando: Favorite Servant (Female/Male)
Gems: Saint Quartz
Apologems: Free Quartz for when the servers are down.
Gacha: Summoning screen (Luck-based/ lottery system used for summoning)
10 Roll: A 30 Quartz roll that gives slightly better odds.
YOLO roll: a single Quartz or Ticket roll
Memeroll: a single Quartz or Ticket roll
Banner: Limited time special summoning opportunity with increased rate for featured Servants and CE.
Rate Up: Do not trust their lies.
F2P: Free to play players
Whale: Players that pay for the server upkeep.
Reroll: Resetting the game by deleting game data (or reinstalling the game) for a chance at better Servants with the initial summons.
Leyline: Dragon Meridian CE
See this topic by /u/FileLoop for nickname origins.
Artoria: Altria Pendragon
Cat: Tamamo Cat
Cockroach: Cu Chulainn
COOL: Gilles de Rais
Dog: Cu Chulainn
Eggplant: Mash Kyrielight
Gudako: Female Protagonist
Gudao: Male Protagonist
JAlter: Jeanne d'Arc (Alter)
Jannu: Jeanne D'Arc
Kiritsugu: EMIYA (Assassin)
KIRA KIRA: Marie Antoinette
Ko-Gil Kid Gilgamesh
Nobu: Oda Nobunaga
REGEND: Sasaki Kojiro
Saber: Altria Pendragon
SAlter: Altria Pendragon (Alter)
Savior of France: Sasaki Kojiro
Umu: Nero Claudius
Waver: Zhuge Liang
|AP||Action Points; Stamina|
|CE||Craft Essence; Equipment|
|CAH||Cursed Arm Hassan|
|DW||Delightful Work; Game Developer|
|F2P||Free to Play Players|
|FP||Friends Points; For Summoning|
|MLB||Max Limit Break; Combining 5 CEs for upgrades to effect|
|MP||Mana Prism; Shop Currency|
|MXH/MHX||Mysterious Heroine X|
|NA||North American Server|
|NP||Noble Phantasm; Special Move|
|NP#||Noble Phantasm levels by combining duplicate Servant cards|
|QP||Quantum Piece; general currency|
|SQ||Saint Quartz; paid summoning currency.|
|ST||Single Target Damage|
|TM||Type Moon; Franchise Creator|