What is the antonym of diameter?

There isn't a single perfect antonym for "diameter." It depends on the context and what aspect of diameter you want to oppose. Here are some options:

General Antonyms:

* Circumference: This refers to the distance around a circle, which is the opposite of the distance across.

* Radius: This is half the diameter, representing the distance from the center of a circle to its edge.

* Width: While not specific to circles, "width" can be used to contrast with "diameter" when discussing the measurement across an object.

Contextual Antonyms:

* Length: If "diameter" is being used to describe the thickness of a cylinder, "length" could be used as an antonym.

* Height: If "diameter" is describing the width of a sphere, "height" might be a suitable antonym.

It's important to consider the specific context when choosing the best antonym for "diameter."