Where once speech was the driving force behind language change, we are moving into an era where writing - or, more precisely, the act of typing on to screens - is a dominant form of verbal interaction. And this has brought with it an accelerating transformation of not only the words we use, but how we read each others' lives.
Consider the emoticon: a human face sketched from three punctuation marks. Born during the course of an early online discussion in 1982, courtesy of computer scientist Scott Fahlman, it addressed one central absence of onscreen words: a human face able to indicate emotional tone.
Fahlman coined two basic expressions - "happy" and "sad" (signalling "joking" and "not joking" respectively) - but further variations almost immediately began to spring up, stretching today into many thousands. Aside from bewildering ingenuity, one thing all of these share is that they are unpronounceable: symbols aimed at the eye rather than at the ear, like an emotionally enriched layer of punctuation.
There's nothing inherently new about such effects. In 1925, the American professor George Krapp coined the phrase "eye dialect" to describe the use of selected mis-spellings in fiction signalling a character's accent without requiring a phonetic rendering of their speech. Mark Twain, for example, used just a handful of spelling variations to convey the colourful speech of his character Jim in Huckleberry Finn (1884), such as "ben" for been and "wuz" for was.
The "z" of Twain's wuz might have a strangely contemporary feel to some readers, courtesy of the so-called "internet z" - a common typo for the letter "s" that has taken on a new life in typed terms such as "lulz", denoting an anarchistic flavour of online amusement via the mangling of the acronym "laughs out loud" (LOL).
While he was a master of visual verbal effects, Twain wouldn't have recognised the strange reversal of traditional relationships between written and spoken language that something like LOL represents. For, where once speech came first and writing gradually formalised its eccentricities, we're now typing some terms and only then learning to speak them.
LOL itself features increasingly in speech (either spelt out or pronounced to rhyme with "doll") together with its partner in crime, OMG (Oh My God!), while some of the more eccentric typo-inspired terms used in online games (to "pwn" someone, meaning to subject them to a humiliating defeat) can't even be said out loud. And if that lies outside your experience, consider the familiarity with which almost all of us now say "dot com" or talk about a "dotcom" business: a web-induced articulation of punctuation that would have inconceivable in any other era.
These may sound like niche preoccupations but, in the past few years, the rise of social media has put what you might call "conversation without speech" at the centre of millions of lives. Every single day sees more than 100 billion emails and 300 million tweets sent. Video, audio and images are increasingly common, too, with more than 72 hours of new video uploaded to YouTube every minute. Yet almost all our onscreen exchanges still begin and end with words, from comments and status updates to typed search queries and the text message.
There's something magnificent about our capacity for cramming emotional shading into even the most constricted of verbal arenas, and making them our own. From text messages with more punctuation appended than most standard paragraphs to tweets with startlingly elaborate subtexts spelled out via hash tags (#gently- selfmocking), our creativity knows few bounds - together with our ability to read between the lines and convert even the unlikeliest sequence of 140 characters into a human story.
Similarly, the democratisation of written words is an astonishing thing, not least because it gifts permanence to so much that has historically been lost - and supplants those speaking on others' behalf with an opportunity to directly encounter every individual's words.
Yet there are hazards and seductions within our ingenuity. As writers, our words belong to the world rather than simply to us, and they can be both read and used in ways we cannot foresee - not to mention aggregated, shared, copied and analysed for far longer than we ourselves may exist.
Then, too, there's the fact that we cannot see or know what the faces behind typed words are actually doing; or what the grand performance of social-media selves conceals as well as reveals. We are, in this sense, vulnerable precisely because of our lavish linguistic talents. We cannot help but read our own meanings into everything we see, forgetting the breadth of the gulf between words and world.
"The man who does not read," Twain once wrote, "has no advantage over the man who cannot read." What might he have made, though, of the man who only reads, or does not know how to listen?
Professionally and personally, we live in an age where the messy self-exposure of speech - of even a conversation by phone or Skype - can seem at once too self-exposing and ephemeral to be useful. Onscreen, typing, the world seems clean and comprehensible; ripe for copying, pasting, sorting and - if necessary - for the most careful construction of even the most spontaneous-seeming quip.
We have never been more privileged as readers and writers, or more finely attuned to the subtexts that can lurk within even a single letter. Yet conversation is an art that must not be supplanted, not least because it reminds us of what the screen cannot say; and of the constant fiction between what is thought, written and understood, and whatever truths lie behind these.
* Tom Chatfield is author of Netymology: a Linguistic Celebration of the Digital World.