1. a small fin-like projection or leaflet, especially one of the ultimate divisions of a pinnately compound leaf
Usage: botanical
2. a small fin or fin-like appendage on certain marine animals
Usage: zoological

Examples

• Each pinnula on the fern frond was delicately shaped and green.
• The botanist examined the pinnulae under a magnifying glass.
• The compound leaf consisted of numerous small pinnulae arranged along the rachis.
• Marine biologists studied the pinnulae on the fish specimen.
• The pinnula structure helps identify different species of ferns.
• Each pinnula contributes to the overall photosynthetic capacity of the leaf.