pinnate

Imagine the leaf of a rose bush or an ash tree. Instead of being one solid piece, it is made of smaller parts lined up along a central stem, like the parts of a feather. That is what pinnate means. The word comes from the Latin "pinna," meaning feather, and it is used most often in botany.

It can describe a compound leaf with many leaflets, or a leaf whose veins spread out from one main vein in a feather-like pattern. You may also see it in zoology for structures that branch in a similar way.

The word pinnate describes something that looks like a feather, especially because its parts are arranged along the two sides of a central axis or stem. It is used mainly in botany to describe the form of leaves, leaflets, and veins. A pinnately compound leaf, for example, is not one single blade. Instead, it has a row of smaller leaflets attached along a main stalk, called a rachis. Rose, ash, and walnut leaves are common examples.

The word can also describe leaf venation. In a pinnate vein pattern, smaller veins branch out from one main midrib in a way that suggests the barbs of a feather. This pattern appears in many familiar leaves.

Beyond plants, you may sometimes see pinnate in zoology for body parts that branch in a feather-like way.

The word comes from the Latin "pinna," meaning feather or wing. So when you see a structure with many parts set along a central line, the image of a feather gives you the key idea. In most cases, pinnate is simply a precise way to say that something in nature is arranged in that feather-like pattern.