Corals are animals that have the structure of a polyp. Other polyps include sea anemones and Portuguese man o' wars.

Coral polyps are attached to the substrate. Substrate can be rock, other corals, marine debris, or other hard surface. Coral polyps are firmly attached to the substrate by a feature called a pedal disc.

A few, dozens, hundreds, and even millions of coral polyps can be attached to an area of substrate. The substrate covered by coral is called a coral branch or coral mound. The community of corals is called a colony.

colony
Noun

group of one species of organism living close together.

Noun

tiny ocean animal, some of which secrete calcium carbonate to form reefs.

coral branch
Noun

area of substrate covered by coral. Also called a coral mound.

Noun

garbage, refuse, or other objects that enter the coastal or ocean environment.

pedal disc
Noun

in a sea anenome or coral, the thin tissue that attaches the animal to the substrate.

polyp
Noun

a type of animal with a fixed base, a tubelike body, and tentacles for catching prey.

Portuguese man o' war
Noun

large colony of organisms, resembling a jelly, with venomous tentacles.

rock
Noun

natural substance composed of solid mineral matter.

sea anemone
Noun

type of marine animal related to corals and jellies.

substrate
Noun

base of hard material on which a non-moving organism grows. Also called substratum.