Corona: a circular structure, or spiked circular structure, surrounding a central core
Corona is the Latin word for a crown. And, after passing through French, it’s the origin of our word crown. In its original form, it’s used to designate all sorts of crown-like structures. The spiky protrusions from the capsule of the coronavirus give it its name. The halos of coloured light often seen around the moon are also referred to as a corona—they are generated by diffraction and interference of light passing through tiny particles in the Earth’s atmosphere. And during a total solar eclipse we are able to see the wispy outer atmosphere of the sun, which is also called a corona.
There are others. The circular chandelier of a church is called a corona lucis, “crown of light”; the tonsure of a Roman Catholic monk is called a corona clericalis, “clerical crown”; electrically charged conductors can cause a halo of ionization in the surrounding atmosphere, called a corona discharge; and there are a host of biological structures, from seeds to brains, that are called coronas because of their shape. We also have two constellations, Corona Borealis and Corona Australis, the northern and southern crowns. Both consist of tightly curved arrays of stars, more reminiscent of tiaras than conventional crowns.
Corona is still the word for “crown” in Spanish, which is why a bottle of Mexican Corona beer has a little picture of a crown on it. (Fatuous early reports that American beer drinkers were avoiding Corona beer because of confusion with coronavirus turned out not to be reflected by reality.) Corona is also the Spanish name for a particular size of cigar, intermediate in length between a robusto (“strong”) and a toro (“bull”), though slimmer than either—there seems to be no particular logic to the nomenclature.
A coronet is a small crown. A coronation is, of course, a crowning ceremony. The person who sets the crown on the royal head is variously styled a coronator or coronant. To coronize is the act of crowning, and a person wearing a crown is incoronate. Something crown-shaped is coroniform, or coronary. The latter word gives its name to the two coronary arteries of the heart, which supply blood to the heart muscle. Their ramifications around the heart make it look, I suppose, a little as if it is set inside a a rather exotic inverted crown.
Something pertaining to a crown is coronal. So in anatomy, we have the coronal suture of the skull, which crosses the head from side to side; and the coronal plane, one of the three principal anatomical planes of the body, which cuts through from side to side and top to bottom.
We often use the phrase “The Crown” to refer to the royal office itself.* A coroner was once a local or regional officer assigned to protect the property rights of the Crown. (Nowadays in England, a coroner’s main role is to hold inquests into deaths caused by violence or accident.)
Corolla is the Latin word for a small crown, or a garland of flowers, and it’s the name applied in English to the petals of a flower. In ancient Rome a corollarium was a small sum of money paid for a garland of flowers; it went on to mean a tip or gratuity. Then, in a metaphorical sense, it became the word for a little extra bit of detail at the end of a mathematical proof—something that followed naturally from the proof already given, which did not require a proof of its own. Which is where the English word corollary comes from, designating something that is an immediate consequence of what has previously occurred or been said.
And finally, have you ever wondered why the military rank of colonel is pronounced in English as if the first “l” is an “r”? The word, and its spelling, comes from Italian colonnello, which is derived in turn from colonna, “column”. So the military rank of colonnello was the person who led a column of men. The French adopted this as coronel—probably just because l’s sometimes change into r’s, especially if there is more than one “l” in a word, but also perhaps under the influence of couronne, “crown”—the French version of Latin corona. But then, in a delayed burst of etymological exactitude, the French word was revised to colonel during the 16th century. English acquired both spellings from the French, but then managed to eliminate the “r” version during the 17th century, while perversely preserving the “r” pronunciation.
* This substitution of an attribute for the name of the thing meant, which is a common enough formulation, is called metonymy. Other examples are “The Vatican”, “The Oval Office” and “The Kremlin”.