When referring to the anatomical structures of birds, the term "lesser wing" typically refers to the smaller of the two wings located on either side of the bird's body. This term can also be used in reference to the skeletal structure of the wing itself. Some synonyms for "lesser wing" include "alula," "bastard wing," and "spurious wing." These words are often used interchangeably and are all used to describe the smaller wing-like structure located near the shoulder of the bird. Regardless of the specific term used, these structures play an important role in the bird's ability to fly and navigate through their environment.