Earth, AS AN ELEMENT
Etymology
The Modern English word Earth developed, via Middle English, from an Old English noun most often spelled eorðe.[25]
It has cognates in every Germanic language, and their ancestral root has been reconstructed as **erþō*.
In its earliest attestation, the word eorðe was already being used to translate the many senses of Latin terra and Greek γῆ gē: the ground, its soil, dry land, the human world, the surface of the world (including the sea), and the globe itself.
As with Roman Terra/Tellūs and Greek Gaia, Earth may have been a personified goddess in Germanic paganism: late Norse mythology included Jörð ('Earth'), a giantess often given as the mother of Thor.[26]
Historically, earth has been written in lowercase.
From early Middle English, its definite sense as "the globe" was expressed as the earth.
By the era of Early Modern English, capitalization of nouns began to prevail, and the earth was also written the Earth, particularly when referenced along with other heavenly bodies.
More recently, the name is sometimes simply given as Earth, by analogy with the names of the other planets, though earth and forms with the remain common.[25]
House styles now vary: Oxford spelling recognizes the lowercase form as the most common, with the capitalized form an acceptable variant.
Another convention capitalizes "Earth" when appearing as a name (for example, "Earth's atmosphere") but writes it in lowercase when preceded by the (for example, "the atmosphere of the earth").
It almost always appears in lowercase in colloquial expressions such as "what on earth are you doing?"[27]
Occasionally, the name Terra /ˈtɛrə/ is used in scientific writing and especially in science fiction to distinguish humanity's inhabited planet from others,[28] while in poetry Tellus /ˈtɛləs/ has been used to denote personification of the Earth.[29]
Terra is also the name of the planet in some Romance languages (languages that evolved from Latin) like Italian and Portuguese, while in other Romance languages the word gave rise to names with slightly altered spellings (like the Spanish Tierra and the French Terre).
The Latinate form Gæa or Gaea (English: /ˈdʒiː.ə/) of the Greek poetic name Gaia (Γαῖα; Ancient Greek: [ɡâi̯.a] or [ɡâj.ja]) is rare, though the alternative spelling Gaia has become common due to the Gaia hypothesis, in which case its pronunciation is /ˈɡaɪ.ə/ rather than the more classical English /ˈɡeɪ.ə/.[30]
There are a number of adjectives for the planet Earth.
From Earth itself comes earthly.
From the Latin Terra comes terran /ˈtɛrən/,[31] terrestrial /təˈrɛstriəl/,[32]
and (via French) terrene /təˈriːn/,[33]
and from the Latin Tellus comes tellurian /tɛˈlʊəriən/[34] and telluric.[35]