1. Resembling or relating to a ray or rays; having a radial structure.
Usage: technical; biology

1. Any of the actinide elements, a series of radioactive metallic elements with atomic numbers 89–103.
Usage: chemistry

Examples

• The actinoid structure of the sea star allows it to move in multiple directions.
• Uranium is the most well-known actinoid element.
• Actinoid symmetry is common in many marine organisms.
• Thorium is another naturally occurring actinoid.
• The actinoid series includes elements used in nuclear energy and medicine.