This word has Middle English and Latin roots and has to do with flow. You could use the word to describe music or a piece of writing. Here’s an example of how the word can be used.
“A few years later, when I learned that Jayne Anne founded the MFA program at Rutgers-Newark, I had to apply. She was the program’s director, and also taught fiction workshops. I loved being in her classes. We read The Bluest Eye by Toni Morrison and Fat City by Leonard Gardner, and she showed us the songs of their lines. Lines was the word she used to describe sentences. No matter their construction, sentences were to be linear and profluent. Subject, verb, object.”- Nick Ripatrazone, Is Line Editing a Lost Art?