The ability of a character to speak or read a language is generally determined by whether they know the language and their Intelligence score or related skills. Here's how this typically works:
1. Language Proficiency
Speak and Understand: If your character knows a language (e.g., Common, Elvish), they are generally considered fluent in speaking and understanding it.
Read and Write: By default knowing a language does not automatically mean the character can also read and write in it unless specified otherwise.
2. Intelligence and Literacy
The extent of a character's vocabulary, eloquence, or literacy for secondary languages depends on their Intelligence score or background.
A character with low Intelligence (e.g., 1-10) will have limited vocabulary or difficulty forming complex sentences, even if they technically know the language. They are unable to read it however.
A character with a medium Intelligence (e.g. 10-15) will have a general understanding and a passable comprehension, but a limited understanding of the written word.
A character with a high Intelligence (e.g., 16 or higher) may have advanced vocabulary, read and write fluently, and potentially understand nuance or ancient scripts.
3. Roleplay
Language fluency can also be flavored through roleplay. For example:
A character might speak with a heavy accent or make grammatical errors if they learned the language as a secondary skill.
A barbarian with a low Intelligence might be able to say only basic phrases in Common, even if they technically know it.
4. Language-Based Skills
Intelligence Checks: Reading or interpreting complex or ancient texts might require an Intelligence (Investigation) or Intelligence (History) check, especially for obscure or archaic versions of a language.
Insight: Understanding subtlety or intent in spoken language might involve a Wisdom (Insight) check, particularly for dialects or coded speech.
5. DM's Discretion
The DM can decide that certain aspects of a language (e.g., dialects, slang, or ancient scripts) are harder to understand, even if the character knows the language. In such cases, Intelligence or other skill checks might be required.
6. Language Learning
Characters can learn additional languages through backgrounds, feats (e.g., Linguist), downtime activities, or magical means. The DM might determine that newly learned languages come with limited fluency until practice occurs.