Pronunciation: [ɹˈat͡ʃa͡ɪz] (IPA) 
The word "rachis" is spelled /ˈreɪkɪs/ and refers to the backbone or central axis of a plant. The spelling of this word can be easily remembered by breaking it down phonetically. The first syllable, "ra," is pronounced /reɪ/, which rhymes with "day" and "may". The second syllable, "chis," is pronounced /kɪs/, which is similar to "kiss" but with a hard "k" sound. Together, the phonetic sounds create the word "rachis" spelled as it is.
The term "rachis" refers to a specific anatomical structure found in biology, particularly in plants and animals. As a noun, it often describes the central axis or backbone of various parts, such as a feather, a compound leaf, or a spikelet in grasses.
In plants, the rachis typically represents the main extension of a structure from which secondary units, such as leaflets or flowers, arise. For instance, in a feather, the rachis is the long, stiff central shaft from which the individual feather filaments or barbs branch out. Similarly, in a compound leaf, the rachis is the main stem-like structure that supports and connects multiple leaflets. In grasses, the rachis refers to the central axis of a spikelet, the basic unit of the inflorescence.
In animals, the term can be applied to various structures that resemble a backbone or central axis. For instance, in biology, the term "rachis" is sometimes used to describe the central shaft of a fish fin or a bird's tail feather.
Overall, whether in the context of plants or animals, a rachis serves as a central support structure, enabling the branching or arrangement of secondary appendages. Its role is crucial in determining the overall structure and functionality of the entity it supports.
In bot., that part of a culm which runs up through the ear of corn; the stalk or axis which bears the flowers in other plants; the stalk of the frond in ferns; the common stalk bearing the alternate spikelets in some grasses; in zool., the vertebral column in mammals and birds.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
The word "rachis" is derived from the Greek word "rhákhis" (ῥάχις), which means "backbone" or "spine". It was originally used in anatomy and botany to refer to the main axis or central structure of things, akin to the spine of a human or the midrib of a leaf. The term entered the English language in the early 19th century.
