A meniscus is a curved upper surface of a liquid in a tube or other container. This curvature is caused by the surface tension of the liquid and the adhesive forces between the liquid and the container walls.
There are two types of menisci:
* Concave meniscus: This occurs when the liquid is attracted to the container walls more strongly than to itself. This results in a curved surface that dips in the middle. Water in a glass tube is a common example.
* Convex meniscus: This occurs when the liquid is attracted to itself more strongly than to the container walls. This results in a curved surface that bulges out in the middle. Mercury in a glass tube is a common example.
Here's an example of how to use the word "meniscus" in a sentence:
"The scientist carefully read the volume of the liquid in the graduated cylinder, making sure to read the level at the bottom of the meniscus."