Oh, I think maybe I see what you mean. In some movies the language spoken is mostly language "a" but sometimes has dialogue in language "b". Sometimes, language "b" appears in subtitles during the theatrical run (like when Sean Connery speaks Russian in the beginning of the Hunt for Red October ... or when Aragorn and others speak Elvish in the Lord of the Rings).
Often, when the DVD is released, the subtitles appear just as they did in the theater ... on the video track itself. Othertimes, they are removed from the video track (where they are harder to read in the smaller size of a TV screen) and placed in a seperate subtitle track ... which is in addition to the normal subtitle track (by which I mean not the closed captions but the subtitle track that only has the transcribed dialogue (and not descriptions of the audio like "spooky music plays").
In this case, you need to select the regular subcaption track (the main language, probably the biggest size file) and any additional tracks with the same language. They might appear as being "forced", which means they play by default without being selected, and are usually smaller files.
Don't make the mistake of taking all "forced" tracks though. If the forced track is in another than "your" preferred language, you won't want it. I had to reburn Band of Brothers because the forced-french kept telling me the same as the included subtitles on the video track, but of course, in french (stuff like the date and location of certain scenes). I'd included it the first time because I thought they'd be the subtitles that had English translations of French Dialogue. Ooops! It was really just subtitles for people listening to the French audio track who presumably wouldn't be able to read the English words that appeared from time to time in the movie.