Abarim Publications' online Biblical Greek Dictionary
The noun δρακων (drakon) means snake, particularly a very large one, and is a synonym of οφις (ophis), see below. In western folklore, dragons came to be depicted as large four-footed beasts with wings, which is most likely the result of an otherwise unrecorded encounter with a dinosaur carcass (or, somewhat more daring, as remnant of a very ancient cultural memory, akin to the otherwise inexplicable phenomena of arachnophobia and regular ophidiophobia).
In the far east and the Americas, dragons are serpentine and commonly fly, and although the reason for this may not be immediately clear, the European dragon might have gotten its wings through cultural osmosis. However, in terms of natural evolution, creatures didn't spring wings because they wanted to fly but because they wanted to protect their brood, and this is the reason why angels have wings: to protect (see our article on αγγελος, aggelos, angel). Hence, ancient mythological depictions of creatures with wings are not creatures that typically fly but creatures that typically protect, which means that the winged dragon was much rather considered a protector than an attacker (see our article on δαιμονιον, daimonion, "demon").
The common Hebrew word for snake is נחש (nahash), which is also the word for copper (in Greek: χαλκος, chalkos), which links the image of the snake rather distinctively to the earliest phase of technological sophistication (also see our article on Nehushtan, the bronze serpent). Likewise, the color red signifies primitivity (hence names like Adam and the Red Sea), which explains why the great dragon of Revelation is red, fiery red even (πυρρος, purros): it signifies primitivity. The identical verb נחש (nahash) also means to divine or soothsay (to draw truths from one's intuition rather than from a basin of sophisticated and developed reason), which gives the snake a spiritual slant. Serpents were commonly associated with water (see our article on Leviathan), and so, in a way, was the προφητης (prophetes), or prophet, who indeed is associated with intuitive knowledge (rather than the logical deductions of later scientific traditions).
All this suggests that in ancient stories, the snake represents the earliest phases of mankind as a social being: a culture in which even the adults have the mental sophistication of modern toddlers, a culture that hasn't yet invented common law, or even property rights (the basis of all complex economy). Such a humanity would have been pretty much the same all over the world. Mankind's pre-speech vocalizations would have had a fantastically broad range, but would have been as wholly intuitive as that of any other animal. That means that a human from Mozambique would have been able to interact with a human from Kenya as easily and naturally as a modern dog from Mozambique is able to interact with one from Kenya.
All through its history, mankind has excelled in wholly accidentally making the greatest discoveries (see our article on the verb αποκαλυπτω, apokalupto, to discover, hence the word Apocalypse, meaning discovery). Modern linguists have shown that our celebrated human consciousness is wholly dependent on our language, which rose like a mist from the spontaneous interactions of the masses (Genesis 2:6-7; see for the mental equivalent of the cognitive cycle our article on νεφελη, nephele, cloud). For eons, huge but thinly spread populations would playfully interact and imitate each other's vocalizations until some visionary few began to recognize patterns of spontaneous synchronization in all the grunting and harrumphing, and realize that with some effort, the masses could be taught to adopt specific words for specific things (Matthew 14:19, see 26:26 and our article on the name Logos).
The chances are excellent that the rock paintings that were found in caves in Europe were literally conversation pieces, and served to establish what folks would call certain depicted animals (Genesis 2:19-20). As we argue in our article on the noun ποιμην (poimen), meaning shepherd, alphabetical script evolved from pictures, and even after alphabetic symbols had had their exodus, the realm of images continued to develop into art, and finally moving pictures and graphic games.
Alphabetic text trains the mind to see meaning in abstractions, which means that text literally changed mankind's mind (Ephesians 4:23). Images do that far less, and in modern times it even has become clear that while watching a movie, the brain switches to sleep mode and experiences the movie like a dream. If technology will evolve the way it has been, it appears that graphic imagery will become the medium of choice to acquire information for a large portion of mankind. Reading and writing abstract texts — and thus the skilled ability to consciously imagine one's own future — will be the prerogative of a select few, whereas the bulk of mankind will choose to be told what to believe, and trained to not imagine beyond what is offered. All this helps to explain the loquacious snake in Paradise, and the Dragon sequence of Revelation 12-13 (also see our article on χξς, ch-x-s, or 666).
Loose words developed into fluidic language, and from language came solid rules, then laws and law enforcement, then central governments by kings and tyrants, and then the birth of democracy and the hallowed republic (see our articles on παρθενος, parthenos, virgin, and ελευθερια, eleutheria, or freedom-by-law; the very purpose of the Gospel, according to Galatians 5:1). But underneath all that solid dry land of reason and sophistication, there still slithers the primitive nature of man the animal — like a serpent in the caves of the limbic system, deep beneath the cerebrum — the man who resorts intuitively to theft and murder rather than pursue the troubled collective state of lawful freedom.
Whenever mankind's institutions of trust are compromised, the great red dragon rears its ugly head and gathers the μωροι (moroi) into tribes and sics them upon whatever bastions of organized reason remain (Revelation 20:8). But the New Jerusalem will come about when all traces of primitivity have been erased (20:10), and mankind's governing structures are wholly in synch with the eternal laws of nature (21:22).
In the New Testament, our noun δρακων (drakon) is used as synonym for διαβολος (diabolos), the slanderous (hence the English word devil) and satan (Revelation 12:9), but read our article on satan for a brief brush-up on the tricky truths of monotheistic satanology.
Perhaps somewhat surprisingly, the noun δρακων (drakon) itself stems from the verb δερκομαι (derkomai), meaning to see (unused in the New Testament; from the PIE root "derk-", to glance or see), presumably on account of the old assumption that snakes stare their pray into submission. That means that the word δρακων (drakon) literally means "the one that sees"; not wholly unworthy of the epithet Lucifer, meaning Light-Bringer. It also brings to mind the names Beer-lahai-roi, meaning the Well Of The Living One Who Sees, and Reuben, meaning Son Of Vision.
It also reminds that Eve "saw that the tree was good for food, and that it was a delight to the eyes" (Genesis 3:6), and that Jesus specifically warned against one's own deceiving eye (Matthew 18:9). Particularly also since Biblical snakes are usually aquatic, also have a look at our article on the verb σκανδαλιζω (skandalizo), to night-fish or hoodwink.
Our noun δρακων (drakon) is used 13 times; see full concordance.
The noun εχιδνα (echidna), viper, is one of two common Greek words for snake — the other being οφις (ophis), serpent, see below. It's not wholly clear where the word εχιδνα (echidna) comes from or how it differs from οφις (ophis), or even if it does (Matthew 23:33), but the latter is more commonly equated with δρακων (drakon), dragon, see above, which suggests that the οφις (ophis) was known for its formidable size and bold appearance, whereas the εχιδνα (echidna) for its smaller size and sneaky or stealthily attack. In the classics the noun εχιδνα (echidna) was proverbial for deceitful and treacherous people. It's used 5 times; see full concordance
The noun οφις (ophis), serpent, is the more common Greek word for snake, and the one most commonly equated with δρακων (drakon), dragon (see above). The word itself stems from a widely attested Proto-Indo-European root "hogis-", but its formation might have been helped along by its associative proximity to the verb οπτομαι (optomai), to gaze at, and the noun ωψ (ops), eye (as δρακων, drakon, relates to δερκομαι, derkomai, to see).
The οφις (ophis) was also — rather surprisingly in a biological sense but not when we consider what happened to Eve (2 Corinthians 11:3) — regarded to be φρονιμος (phronimos), or "prone to cast feelings very precisely into words, definitions, schemas and types, to serve as the building elements of much larger constructions", as we ourselves so eloquently put it in our article on that particular adjective (Matthew 10:16). Serpents could be poisonous or constrictive, in either case dangerous to handle of step on (Mark 16:18, Luke 10:19, John 3:14).
This noun οφις (ophis), serpent, is used 14 times; see full concordance.