Many of the threads on this focus on speaking. Other threads focus on understanding/speaking new languages that the Beast knows but the character does not know. I'm not interested in these questions.
My question is: Can a druid, while Wild Shaped, understand language. And if so, which ones?
There are two relevant lines from the PHB:
Your game statistics are replaced by the statistics of the beast, but you retain your alignment, personality, Intelligence, Wisdom, and Charisma scores. You also retain your skill and saving throw proficiencies, in addition to gaining those of the creature. (PHB, Druid Class Section, Wild Shape subsection)
You retain the benefit of any features from your class, race, or other source and can use them if the new form is physically capable of doing so. (PHB, Druid Class Section, Wild Shape subsection)
If language is a "game statistic" - then your language(s) would be "replaced" by the one's in the Beast's stat block. Language is in every Beast's stat block, so you would lose all languages except those in the Beast's stat block. I'm not sure I agree with this, but it's one interpretation.
The above interpretation conflicts with the second line: You retain the benefit from your class/race/etc (which includes languages).
Although, perhaps "physically capable" means that you wouldn't understand language unless the Beast could. Speaking from common sense and my basic understanding of biology, my brain is what makes me physically capable of understanding language. Without that, I couldn't understand anything. Some animals have more sophisticated brains than others. Some can partially understand language (dogs, maybe), others: not at all. The difference lies in their circuitry, their brain complexity and capacity, is different. This is a physical difference. A physical capability, you might say. Interpreting the second line this way resolves any conflict between the two lines: You only understand the Beast's language proficiencies, and you don't retain other languages because the Beast is not physically capable of doing so. However, if the Beast is physically capable of understanding some languages, then it must be physically capable of learning others (to some degree). Therefore, it's not a physical capability.
Conclusion: Those interpretations must be wrong. Okay, so let's look at alternatives.
- Language is a "Skill Proficiency" and is therefore retained, as per the first line of rules above. I don't like this. Language is never coupled with Skill in the PHB. There are "Language Proficiencies" and "Skill Proficiencies." They are not the same.
- Your intelligence is the source of your language understanding, and since you keep your Intelligence stat, you should keep your languages. Not true, at least not in 5e. Low intelligence might make you worse at speaking, but we're not talking about speaking.
I think perhaps the rules don't actually address it, so it's left to DM discretion, yes?