Through in modern usage our planet’s Latin name, Terra, appears only in science fiction, the adjective terrestrial is often employed to refer to phenomena associated with Earth or with land as opposed to water. It is also the root of extraterrestrial, the term for any (so far conjectural) life-form that does not originate on Earth, or for anything existing or occurring beyond the planet.
Terrestrial also refers to the inner planets of the solar system as a category. (See the next entry for the classification for the outer planets.) It can also mean “mundane,” as does terrene, which has the additional sense of “earthly.” (Terrene is also a noun referring to the planet or its terrain — and that word, like terrarium, also stems from the Latin term terrenum.)
Jovial means “jolly, convivial” — not traits associated with a god normally generally depicted with a stern visage. However, this is the word medieval astrologers used to describe those characteristics, which they ascribed to the influence on the planet on human behavior. The adjectival form for referring to the god or to the category of gas giants typified by the planet Jupiter is Jovian; this is also the term for referring to the planet’s natural satellites in fact and fiction and to fictional inhabitants.
Because of its belligerent-looking red glow, Mars was associated in ancient times with conflict, and the Romans named it after their god of war. The adjective martial (“martial law,” “martial arts,” court-martial — the hyphen in the last word is a holdover from the term’s French origin) refers to war and fighting.
Someone with an unpredictable or volatile personality is said to be mercurial, thanks to an association with Mercury, the swift messenger of the Latin gods. (The liquid element mercury, also known as quicksilver, was perhaps given that name because of its rapidly free-flowing quality.) But the adjective is also associated with eloquence and ingenuity, as well as larcenous behavior. Why? The god Mercury was considered the protector of thieves as well as merchants and travelers, who would appeal to the deity to favor them with speed. The planet Mercury was so named because of its fast orbital velocity.
Like Terra, Luna, the Roman name for the Moon, seems to appear only in science fiction these days. But lunatic, meaning “foolish” or “insane,” is common, albeit mostly in the nonclinical sense. (Lunacy, another word for insanity, and the adjectival form derive from the onetime notion that phases of the Moon affect mental instability.) Lunar, however, is the adjectival form for scientific references to Earth’s natural satellite.
The Roman god said to have been the father of Jupiter was associated with traits opposite to those of the scion who usurped his rule; a saturnine person is gloomy, sardonic, and surly, as opposed to the jovial type, though the adjective also has the neutral sense of “sluggish” and “serious.” This temperament was said in the Middle Ages to be the influence of the planet farthest from the Sun (or the one believed at the time to be the most remote) and the slowest.
But the god was also identified with justice and strength, as well as with agriculture, and later was celebrated in the weeklong winter-solstice feast known as the Saturnalia, when the rules of moral conduct and social status were suspended. That name, with the initial letter lowercased, now refers to any unrestrained merrymaking.
A supposed inhabitant of Venus is a Venusian, of course, but another term influenced by the name of the Roman goddess of love and beauty may surprise you. Because of Venus’s association with sex as well as affection and attractiveness, her name was the inspiration for venereal, which means “relating to sexual pleasure or indulgence” but is almost exclusively employed to refer to sexually transmitted infections or diseases.
However, another variation has a more positive association: To venerate is to admire, honor, or respect (the noun form is veneration), and venerable refers to someone or something considered deserving of one of those types of regard. It is also synonymous with sacred and can apply to a person, place, or thing that through age and/or accomplishments earns esteem.