1. Plural of pinnula; small leaflets or branches arranged on either side of a compound leaf or frond, especially in ferns and some flowering plants.
Usage: botanical term; plural form
2. In zoology, small fin-like or feather-like structures on certain marine organisms, such as sea stars or brittle stars.
Usage: zoological term; plural form

Examples

• The fern's frond is divided into pinnae, each of which bears numerous pinnulae.
• Botanists examined the pinnulae under a microscope to identify the plant species.
• The delicate pinnulae of the compound leaf create a feathery appearance.
• In some brittle stars, the pinnulae help with feeding and movement along the seafloor.
• The arrangement of pinnulae on the rachis is an important characteristic for plant classification.