[RPG] What are the different PC languages for 2nd edition AD&D

There are major differences, but nothing too insurmountable.

• AD&D 1E adds non-weapon proficiencies in DSG, WSG, and OA, while they are core in AD&D 2E
• 2E allows points to be spread amongst thief skills, rather than using a fixed table per skill.
• 2E groups classes differently, and lacks the assassin and monk.
• Minor differences in several tables
• several spell changes.
• minor NWP changes
• Psionics are incompatible between editions - pick one, and only one, and use it exclusively.
• 1E Class List: Fighter, Magic User, Cleric, Illusionist, Thief, Druid, Paladin, Ranger, Monk, Assassin, Fighter/Thief/Bard; adding UA adds thief-acrobat, Cavalier and Barbarian. Dragon adds a dozen or more NPC classes of various quality levels. DLA adds 4 classes of knights ad 3 of wizards, plus tinkers. OA adds several oriental classes as well
  2E class list Fighter, Magic User, Cleric, Thief, Bard, Paladin, Druid, Ranger, PsiHB adds Psionicist. Sages and Specialists adds a dozen NPC classes, all pretty consistent power levels, and many playable as adventurers. Dark Sun adds a few more classes, including Gladiator, and in Dragon Kings, adds more thief abilities; the Thief abilities are in some later 2E Player's Option series books.

Most 2E DM's used some 1E materials. THe key is picking your core edition, and what you'll cross over. Monks and Assassins crossed over VERY easily. DSG/WSG non-character rules can be used as is.

Again, Pick your reference edition: the rules are subtly different in many places, and it trips people up. So use one as your ruleset, but allow the stuff you want from the others as a port-in.

Also, note that monsters from other 3E/3.5E/PF can be used easily enough simply by looking up THAC0 from HD, finding the AD&D AC by taking 20–(d20 AC), and spells directly across by name (even when they do very different things).

Note also, porting in monsters from 5E is equally as doable, with the same basic caveats as from d20. Advantage/Disadvantage is also easily imported. Magic weapons and armor are far less portable, because the scale of AD&D magic items is +1 to +5, with a few very rare +0's; 5E is +0 to +3, and +0 with a bonus of some kind is extremely common (eg: Flametongue weapons are +0 to-hit, but do +2d6 fire damage).

In general in play they were ignored or just treated as an abstract language with no further comment.

As to where they came from, here's an answer from Gary Gygax on Dragonsfoot!

As D&D was being quantified and qualified by the publication of the supplemental rules booklets. I decided that Thieves' cant should not be the only secret language. Thus alignment languages come into play, the rational [sic] being they were akin to Hebrew for Jewish and Latin for Roman Catholic persons.

I have since regretted the addition, as the non-cleric user would have only a limited vocabulary, and little cound [sic] be conveyed or understoon [sic] by the use of an alignment language between non-clerical users.

If the DMs would have restricted the use of alignment languages--done mainly because I insisted on that as I should have--then the concept is vaible [sic]. In my view the secret societies of alignment would be pantheonic, known to the clerics of that belief system and special orders of laity only. The ordinary faithful would know only a few words, more or less for recognition.

In other words, it was supposed to be more like religious languages, but wasn't really well thought through. It disappeared in Second Edition and was not missed.