Here are some examples:
* Submarine: A vessel that operates beneath the surface of the water.
* Subterranean: Located or occurring beneath the surface of the earth.
* Subordinate: Of lower rank or position.
* Subdue: To conquer or overcome.
* Substandard: Below the accepted or expected standard.
However, "sub-" can also take on more specific meanings depending on the context. For example:
* Subtropical: Relating to a region or climate that is located just north or south of the tropics.
* Substitute: A person or thing that takes the place of another.
* Subdivide: To divide something into smaller parts.
It's important to consider the specific word and context to determine the precise meaning of "sub-".