Abarim Publications' online Biblical Greek Dictionary
The adjective ταχυς (tachus) means quick or swift and is the opposite of βραδυς (bradus), slow. It's formally unclear where this word may have come from. There is no obvious Greek noun that describes a proverbial fast thing (the noun ταχος, tachos, speed, derives from our adjective; see below), and likewise no Proto-Indo-European root that may have yielded our adjective.
But the Greek alphabet derives from the Hebrew one, and here at Abarim Publications we often propose that along with the alphabet, the Greeks also imported some basic abstract terms, to jump-start the later so celebrated Greek sense of abstraction (see our lengthy article on Hellas for more on this). Hence, a much more likely candidate for the source of our Greek adjective is the Hebrew verb חוש (hush), to hurry or hasten, and more specifically its derived noun תחש (thahash), meaning "hurrier," the word for some animal whose hides provided the outer cover of the tabernacle (Exodus 26:14) — see our article on the name Thahash.
Note that the Hebrew letter ח (heth) often transliterates into Greek as the χ (chi). The name Ahab, for instance, is אחאב ('ah'ab) in Hebrew, Αχααβ (Achaab) in the Greek Septuagint, and Achab in the Latin Vulgate. Likewise, the name Thahash, hurrier, is תחש (tahash) in Hebrew and Τοχος (Thochos) in Greek, albeit Tahas in Latin.
From our adjective ταχυς (tachus), quick, comes the invented term tachyon, which describes a hypothetical particle that always travels faster than light — which requires it to have negative mass, which obviously makes it not-a-particle. A particle-that-is-not-a-particle can obviously not exist in the material universe, but since the human mind is both massless and capable of traveling back in time (when we review past events, which is really all a consciousness does) we here at Abarim Publications like to go on record as to postulate the tachyon as quantum of mind. A thought experiment is in order:
Imagine two physicists who want to measure the speed of light. For this they have built an installation that makes it possible to wait for an electromagnetic signal to arrive after it was sent from its source, when the sending physicist pushes the send-button. Here's the catch: there is nothing in the material universe than can run ahead of that signal, so as to warn the measuring physicist that something is coming. Only a plan hatched by clever humans can result in something waiting for light to arrive. All other beings in the universe are always surprised by the arrival of light. That means that a scheming human mind is able to outrun light, and thus goes faster than light and thus goes back in time.
Since a contemplative mind thinks in words, and words are required to entertain conscious thoughts, words are tachyons. Societies that have no script usually only have words for things that can be seen and pointed at (so as to agree upon what to call those objects). For a society to entertain abstract things (love, anger, war, heaven), a script is required that gives these things physical reality (a written word) to point at. Pre-script societies solve this problem by inventing gods, but as soon as script takes on the role of giving physical reality to abstract things, deities quickly go out of vogue. But ultimately, words are massless things that form a continuum in which journeys faster than light, and thus journeys into the past, are perfectly possible.
Because of their negative mass, tachyons can only be spiritual and cannot be material (tachyons are pneumatons, if you will). Particles that have zero mass and thus travel as fast as light (photons and gluons, and possibly gravitons) have been lovingly dubbed luxons, after the Latin lux and the Greek λευκος (leukos), both meaning light; see the names Luke and Lucifer. Particles that have positive mass and thus travel slower than the speed of light (that's pretty much all of the rest of them) are called bradyons.
Our adjective ταχυς (tachus) occurs just once in the New Testament, namely in James 1:19 only, but from it derive:
- The adverb ταχα (tacha), meaning swiftly, presently or promptly (Romans 5:7 and Philemon 1:15 only). In the Greek classics this word was frequently deployed to express contingency from a probability (in the elegant terms of Liddell and Scott), to be translated with "perhaps", which is how it appears in Paul's letter to Philemon. But perhaps Paul's remark even refers to the whole of the reality in which speed is a thing: namely in the world governed by time. Paul also seems to say that Philemon lost Onesimus in our time-bound world, but received him back for eternity, which is a spiritual continuum not governed by time.
- The adverb ταχεως (tacheos), meaning shortly, speedily, soon, hastily. It's used 10 times; see full concordance.
- The adjective ταχινος (tachinos), meaning quick, swift or impending (2 Peter 1:14 and 2:1 only).
- The adverb ταχιον (tachion), which actually derives from the comparative form of ταχυς (tachus), and thus means more quickly, more swiftly, even more suddenly, or with more haste than usual (hence the tachyon, the particle that goes "faster than" lightspeed and thus backward in time). This adverb is used 5 times; see full concordance.
- The adverb ταχιστα (tachista), which actually derives from the superlative form of ταχυς (tachus), and thus means most quickly, most swiftly, most suddenly (Acts 17:15 only).
- The noun ταχος (tachos), meaning speed or speediness, swiftness or expedience. In the classics this word was sometimes used to describe quickness of temper, volatility of mind or quickness of apprehension. And sometimes it was used to describe any sort of general sameness: people or things of similar "speed" were similar in many defining ways. Our noun is used 7 times, and always in the dative: to speediness, or: so-as-to-be-quick; see full concordance.
- The adverb ταχυ (tachu), meaning quickly, or hastily. This word is actually the adverbially used neutral singular of ταχυς (tachus). It is used 12 times; see full concordance.