I'm writing a villanelle as a school project and one of my lines is too short. Can somebody give me tips on how to extend the line?
A line that refuses to be the right length is one of the struggles with writing poetry. Here's how I (try to) deal with it.
Consider what it is you're saying, in that line, and in the lines around it. Can you use different words to express the same idea? Can you replace a word with a longer synonym? For one syllable, can you add some interjection, like 'oh' or 'lo!'? If you're lacking more than one syllable, perhaps you can add some sort of 'and X'? Can you add an adjective to a noun, or an adverb to a verb?
In the end, it all boils down to try to say the same thing using different words.