As per RAW, there are standard languages and exotic languages. You are supposed to need permission from the DM to take the exotic languages, but the rules do not give guides for them. Note, the standard languages are much more useful at lower levels, but become much less so at higher levels, while the exotic ones are the reverse.
Here are my house rules for when to let players take exotic languages. Note, in certain campaigns, I have ruled that even a standard language would need special circumstances, so you might do the same.
Feel free to comment or argue, if you desire.
Exotic Languages:
Firstly, any Ranger that has Favored Enemey may take the language of their 1st level favored enemy. Also these rules do not over-ride specifically granted languages, i.e. a kobold always knows draconic. In addition, a Horizon Walker Ranger can take any of the exotic languages except for Undercommon and Draconic.
Secondly, when I mention classes, it refers to the class of your TEACHER, which, under some circumstances, may not be exactly the same as your own. In particular, Warlocks and Sorcerers are known for training people of the same class but a different subclass, because of how rare they are. You may be the only Hexblade Warlock in the country.
Abyssal and/or Infernal. Abyssal is the language of Demons and other Chaotic Fiends. Infernal is for the Devils and other Lawful Fiends. Both use the Infernal alphabet. . In order to learn either you usually need to have trained by someone famous for: hunting Demons (usually a Paladins, Monster Slayer Ranger, Cleric), someone that summons Demons (usually Clerics, Sorcerers, Wizard or Warlock) or any Fiend, Undead or Undying Warlocks or actively seeking to be trained by them. In those cases, it WILL affect your reputation as well as theirs.
Celestial. The language of the Divine. Any Cleric, Star Druid, Land Druid, Monk, Paladin, Celestial Warlock or Divine Sorcerer can learn these. Also, any person whose background was religious, i.e. Acolyte, Hermit, etc. may learn this language.
Draconic. The language of Dragons, Dragonborn, and Kobolds. Obviously any dragonborn or kobold already knows this . Also any Ascendent Dragon Monk, Drakewarden or Monster Slayer Ranger, Draconic Sorcerer, Druid if (Land, Moon, Shepard, or Wildfire), Lore Bards, or Wizard.
Deep Speech. The language of Abberations. Any Spore Druid, Great Old One Warlock, Monster Slayer Rangers, Psi warrior fighter, Soul Knife Rogue, Abberant Mind Sorcerer, or Wizard may learn these languages.
Primordial: The language of the elementals. Note it has some sub-types that are understandable with difficulty (i.e. Aquan, a water version). Think Australian English vs that of an Irishman). Artificers, Wizards, any Druid, Four Elements Monk, Lore Bard, Storm or Wild Sorcerer, or a Fathomless or Genie Warlock, may learn this
Sylvan: The language of the Fey and the ancestral language of the elves. Any Gnome, Elf, Barbarian, Bard, Druid, Fey Wanderer Ranger, any Monk, Ancient Paladin, Shadow Sorcerer, archfey or Hexblade Warlock,
Undercommon: The language used in the Underdark. Gloom Ranger, any Rogue, any Halfling, dwarf or gnome and any necromancer Wizard may speak this language.
As per RAW, there are standard languages and exotic languages. You are supposed to need permission from the DM to take the exotic languages, but the rules do not give guides for them. Note, the standard languages are much more useful at lower levels, but become much less so at higher levels, while the exotic ones are the reverse.
Here are my house rules for when to let players take exotic languages. Note, in certain campaigns, I have ruled that even a standard language would need special circumstances, so you might do the same.
Feel free to comment or argue, if you desire.
Exotic Languages:
Firstly, any Ranger that has Favored Enemey may take the language of their 1st level favored enemy. Also these rules do not over-ride specifically granted languages, i.e. a kobold always knows draconic. In addition, a Horizon Walker Ranger can take any of the exotic languages except for Undercommon and Draconic.
Secondly, when I mention classes, it refers to the class of your TEACHER, which, under some circumstances, may not be exactly the same as your own. In particular, Warlocks and Sorcerers are known for training people of the same class but a different subclass, because of how rare they are. You may be the only Hexblade Warlock in the country.
Abyssal and/or Infernal. Abyssal is the language of Demons and other Chaotic Fiends. Infernal is for the Devils and other Lawful Fiends. Both use the Infernal alphabet. . In order to learn either you usually need to have trained by someone famous for: hunting Demons (usually a Paladins, Monster Slayer Ranger, Cleric), someone that summons Demons (usually Clerics, Sorcerers, Wizard or Warlock) or any Fiend, Undead or Undying Warlocks or actively seeking to be trained by them. In those cases, it WILL affect your reputation as well as theirs.
Celestial. The language of the Divine. Any Cleric, Star Druid, Land Druid, Monk, Paladin, Celestial Warlock or Divine Sorcerer can learn these. Also, any person whose background was religious, i.e. Acolyte, Hermit, etc. may learn this language.
Draconic. The language of Dragons, Dragonborn, and Kobolds. Obviously any dragonborn or kobold already knows this . Also any Ascendent Dragon Monk, Drakewarden or Monster Slayer Ranger, Draconic Sorcerer, Druid if (Land, Moon, Shepard, or Wildfire), Lore Bards, or Wizard.
Deep Speech. The language of Abberations. Any Spore Druid, Great Old One Warlock, Monster Slayer Rangers, Psi warrior fighter, Soul Knife Rogue, Abberant Mind Sorcerer, or Wizard may learn these languages.
Primordial: The language of the elementals. Note it has some sub-types that are understandable with difficulty (i.e. Aquan, a water version). Think Australian English vs that of an Irishman). Artificers, Wizards, any Druid, Four Elements Monk, Lore Bard, Storm or Wild Sorcerer, or a Fathomless or Genie Warlock, may learn this
Sylvan: The language of the Fey and the ancestral language of the elves. Any Gnome, Elf, Barbarian, Bard, Druid, Fey Wanderer Ranger, any Monk, Ancient Paladin, Shadow Sorcerer, archfey or Hexblade Warlock,
Undercommon: The language used in the Underdark. Gloom Ranger, any Rogue, any Halfling, dwarf or gnome and any necromancer Wizard may speak this language.