We only mention them to let them know we know they're there. The cause of perfume disappearing is evaporation. Evaporation gets blamed for a lot of things people forget to put the top on. Water vapor gets together in a cloud. When it is big enough to be called a drop, it does.
Mushrooms always grow in damp places, which is why they look like umbrellas.
Momentum is something you give a person when they go away. A monsoon is a French gentleman. To keep milk from turning sour, keep it in the cow. When planets run around and around in circles, we say they are orbiting. When people do it, we say they are crazy.