A few days ago, an article I was subediting used the word instantaneously in conjunction with transmitted – I can’t remember which way round. I started wondering if there is any distinction between instantaneously and the shorter instantly, if there is, then what is it, and if there isn’t, whether I should change it anyway. Dictionary.com defines instantaneous as:
occurring, done, or completed in an instant:
an instantaneous response.
existing at or pertaining to a particular instant:
the instantaneous position of the rocket.
It defines instant (as an adjective) as:
succeeding without any interval of time; prompt; immediate:
instant relief from a headache.
pressing or urgent:
noting a food or beverage requiring a minimal amount of time and effort to prepare, as by heating or the addition of milk or water, before being served or used:
instant coffee; instant pudding.
occurring, done, or prepared with a minimal amount of time and effort; produced rapidly and with little preparation:
an instant book; instant answers; instant history.
designed to act or produce results quickly or immediately:
an instant lottery.
Older Use. of the present month:
your letter of the 12th instant.
the instant case before the court.
In some cases there, instantaneous and instant are not interchangeable. I’m not sure I’d like to drink instantaneous coffee.
Google Ngrams shows that instantaneous is most often followed by velocity, rate, value, power, values, change, voltage, death, axis and effect and instant by case, coffee, success, death, action, relief, use, flight, destruction and execution. Instantaneously is most often used before be, killed, transmitted, destroyed, felt, followed, converted, changed, produced and seized, and after be in various forms, died and killed, while instantly is most often used before before be, made, set, sent, seized, put, took, killed, ordered and followed, and after be in various forms and modal verbs.
–aneous is a comparatively rare suffix in English. This site lists 80 words ending with –aneous, compared with 1179 ending with –eous and 5393 ending with –ous.
25 of these are variations on cutaneous (of, relating to, or affecting the skin) though it doesn’t list cutaneous itself. The spell-checker on Pages for Mac recognises only percutaneous and transcutaneous, but with a bit of medical knowledge, most of the rest are guessable.
Alongside instantaneous and instant, a number of other words have shorter alternatives: extraneous (which that site similarly doesn’t have) and extra, contemporaneous (again, not on this site) and contemporary, extemporaneous and extemporary, subterraneous (recognised by Pages for Mac and WordPress) and subterranean, mediterraneous (not recognised) and mediterranean, membraneous and membranous. Generally, the shorter word is used more, but Google Ngrams shows that subterraneous, mediterraneous and extemporaneous are more common than subterranean, mediterranean (lower case) and extemporary. Upper-case Mediterranean is far more common.
The other words recognised by Pages for Mac but which don’t have a shorter alternative are coetaneous (belonging to the same age, era or period, which doesn’t seem to do anything that contemporaneous and contemporary don’t), spontaneous, porcel(l)aneous (relating to porcelain), succedaneous (relating to a succedaneum, a substitute) and miscellaneous. Not on that website but well-known is simultaneous. (So a major word-related website doesn’t have five not-uncommon words.)
Of the remaining words, only consentaneous (agreeing, accordant; done by common consent, done, unanimous) is recognised by Dictionary.com, though dissentaneous is surely its antonym. Some of the rest are guessable, and some not – subtegulaneous anyone (actually, it means under the roof or eaves, indoors – from tegulare, tiles for a roof). A quick search returns about 2,930 results. Of the first 50, 48 are dictionaries etc. The remaining two are a book from 1906 self-consciously demonstrating “epistolary sesquipedalian lexiphanicism” and an Instagram post by someone whose English is occasionally idiosyncratic.
I did all that research after I’d decided to change instantaneously to instantly. Instantaneously wasn’t/isn’t ‘wrong’, but all else being equal, I’ll go for the shorter choice nine times out of ten. In fact, I have just found now that transmitted is one of those verbs which is actually more often used with instantaneously.
PS I use Dictionary.com because it’s convenient, not because it’s (necessarily) always right.