I know that in Biblical Hebrew, take a word like "Vaydaber." "Yedaber" = "He will speak"; the "v" flips the word from future tense to past, so it's "he spoke."
Most translations understand the "v" ALSO means "and"; so in most translations of the Bible (Jewish included), you'll see:
And the Lord spoke ...
Though R' Aryeh Kaplan's translation leaves out the "and"s. (Is that him just making it more readable in common English? Or that the vav's were never intended as "ands"?)
I suppose one could hold "the vav sometimes means and" instead of "always does" or "never does" too.
What are our sources on this?