Here's a breakdown:

* Clastic sediments are formed from the breakdown of pre-existing rocks.

* Gravel consists of rock fragments larger than 2 millimeters.

* Sand consists of rock fragments between 2 millimeters and 0.0625 millimeters.

* Mud consists of particles smaller than 0.0625 millimeters, including silt and clay.

So, when you're talking about these different particle sizes derived from rock weathering, you can use the term "clastic sediments".