Speak Language (INT) is now a linguistics type skill, so taking ranks is beneficial more than ever. During character creation, base and bonus languages still stand as per SRD. Every language has 3 parts: vocabulary, grammar, and script (V, G and S). Every language will have a DC and fluency target assigned. When learning a language, you have to hit the fluency target of each part you want to learn to know the language in that way. Once all three are known, then Mastery can be learned, which lowers the DC and fluency targets of related languages. When trying to learn a language, you must have someone serving as a teacher and/or learning guides (MW skill tool, size and shape of spell books), which increase your skill check by 1 per 4 above their skill check (teacher) or +1 (materials). For every point above the DC of your skill check, one point goes toward fluency. If you stop work for 2 weeks or more, you lose 1 point per day until you resume study.
Easy languages have DC 10 and fluency at 100,
Normal is DC 12 and 200,
Hard Languages are 14 and 400,
Rare Languages are 16 and 600,
Dead Languages are 18 and 800.
Common is easy, Hadansi is Hard, High Hadansi is Rare. The language of the Lost Visitors is a dead language and suffers an additional +8 to DC due to its alien nature and lack of definitive source material or fluent teachers. Teachers may only give benefit to learning if they have achieved fluency at the level the student wants to learn.
Skill checks can be made once a day and no more than INT bonus languages can be studied simultaneously.
Any part of a base or bonus language can be given up for part of another language. So, for example, a Barbarian character can give up mastery and literacy in the three languages he knows to learn grammar and vocabulary in three more languages, effectively making him illiterate and doubling his conversational fluency.
Also, dungeon crawlers might take script in numerous languages and never bother with grammar or vocabulary.
Avid linguists might master one language with a script shared by other tongues to shortcut learning those others, unless the script is the same but applied differently to oral sounds.