Bonjour Bonnie ! The general rule here is as such: - Never pronounce the "s" when "plus" has a negative meaning (no more, no ... left): "Je n'ai plu[s] de beurre." (I have no butter left) but - Pronounce it in positive context most of the time, though it can be omitted: "Il y a de plus en plu[s] / de plus en pluS de pollution." (more and more) The only cases you need to pronounce it is when the meaning could be either negative or positive, for clarity. For example, when using "ne...plus", as a lot of people would drop the "ne" in speech: "Je fume plu[s]." = Je ne fume plus. = I don't smoke any more. "Je fume pluS." = I smoke more. Here are links to our related lessons: De plus en plus de / de moins en moins de + [nom] = more and more / less and less + [nouns] (Comparisons in French) Plus de ... que/Moins de ... que/Autant de ... que = More ... than/Less ... than/As much/many ... as (Comparisons with Nouns in French) N'avoir plus de = To have none left (French Negations) I hope that's helpful! À bientôt !