Could you explain the meaning and role of "for"? I have a hard time understanding the structure.
"For" is used as a conjunction here to link two sentences together. However, "for" cannot be used as a conjunction at the beginning of a sentence, but this sentence is actually a continuation of the previous sentence in the video. So the full sentence here should be, "you must go and visit him at once, for we may not visit if you do not." The word "for" here is similar to "because", though it is a much more formal word to use than "because". This word is a little bit outdated, and it is not very common to use in this context anymore. Here's a few examples of "for" in this context: Ex: She should go see a doctor for she is sick. Ex: I can't have dairy for I am allergic.