Actinal

Part of speech: adjective

Definitions

1. Of or pertaining to the side of a radially symmetrical animal where the mouth is located
2. Relating to the oral or mouth-bearing surface of a radiate creature such as a starfish or sea anemone
3. Describing the aspect of a radiating organism that contains or faces toward the mouth

Etymology: The adjective "actinal" was coined by the Swiss-born naturalist Louis Agassiz, who needed a term for the side of a sea creature that faces the mouth and the ray-like structures around it. He built it from the Ancient Greek "aktis", meaning "ray", the same root that gave English "actinic" and "actinism". The word is therefore a Greek noun with the English adjectival suffix "-al" attached, a deliberate scientific construction rather than a word that drifted into use over centuries. The coinage was aimed at describing animals such as sea anemones and starfish, whose bodies radiate from a central point. Agassiz's term let zoologists refer precisely to the surface around the opening in such creatures, and it stayed in technical biological writing from that point on.

Synonyms: oral

Antonyms: abactinal