What term means reef-building coral, opposite of ahermatypic coral?

The term for a reef-building coral, opposite an ahermatypic coral, is hermatypic.

Hermatypic corals build reef structure by depositing hard calcareous skeletons. Over generations, living colonies, dead coral skeletons, and trapped sediment accumulate into the framework of a reef. The word describes an ecological role rather than simply a body shape or habitat.

Many hermatypic corals contain symbiotic photosynthetic dinoflagellates historically known as zooxanthellae. Their photosynthesis supplies energy that supports rapid calcification in clear, sunlit water. However, hermatypic does not mean “coral that contains zooxanthellae”: some non-reef-building corals have these symbionts, and some deep-water reef builders lack them.

Ahermatypic means non-reef-building. The distinction is also separate from terms such as benthic, pelagic, and nektonic. Those describe where an organism lives or how it moves, whereas hermatypic identifies whether a coral contributes materially to reef construction. Most hermatypic corals are scleractinians, or stony corals, but the ecological label is the key idea.