The difference between ‘la’, ‘la la’, and ‘la la la la’

One syllable, repeated. The number of repetitions is the entire message.

• La. Okay. Acknowledged. Neutral, faintly formal — this is what you say to a shopkeeper.
• La la. Right, understood, moving on. Mildly warm. The workhorse.
• La la la. Yes, yes, fine. I am agreeing mainly so that this can end.
• La la la la. The phone call is over. You both know it. Neither of you has said goodbye, because nobody says goodbye — you simply raise the repetition count until one of you hangs up.

Five is possible but rare, and signals real impatience. Anything past five is a parent.