I am currently working on a fantasy novel in which one of the main characters is a nobleman and scholar, studying exotic languages as part of his higher education and translating documents for the city library in his spare time. The fact that he is fascinated by languages is important to his personality and characterization, and thus the constructed languages I've devised for the setting are more prominent in the plot than they would otherwise be - they're not just there for flavor or worldbuilding flair, in other words.
In particular, there is a Latin-inspired language that features heavily in the books and culture of the world. I try not to "dump" this exotic language on the reader, or spend an inordinate amount of time explaining its syntax and grammar; the reader's main reference for this language comes from the scholar character, and it is only explained or translated as needed for each scene. However, it is significant to the world and spoken with varying degrees of fluency by a number of characters.
Should I include an appendix of common words in this language? Will a language reference be helpful to the reader in any way, or will it just bog the reader down in unnecessary information and excessive worldbuilding?
I have read some other fantasy books that do this, i.e. Eragon, but was wondering about this site's consensus on the topic.
I want to do this for a number of reasons, but the main reason is that the other main character does not speak this language at all, and at some point he tries and fails to communicate with a person who only speaks in that language, which I use to contrast this character's "street smarts" with the scholar character's "book smarts." Obviously the POV character will have no idea what they are hearing, and thus, since I'm writing the chapter from this person's point of view, there's no obvious way to convey to the reader what's being said unless I provide an out-of-story reference.