Sometimes a full stop in a text is simply the end of a sentence. Other times, it can signify crossed wires, an angry boyfriend or a pile of dirty dishes left in the sink.
It is 25 years today since the first text message was sent to a mobile phone.
And it has been 25 years of anxiety about what we text and whether it is changing how we communicate.
Is an exclamation point too friendly or just right? Is "text speak" the reason why your 13-year-old will never write like Shakespeare?
Neil Papworth is the person who inadvertently helped start this language revolution.
He sent what is believed to be the first-ever text message from a big, draughty switch room in the UK to a Vodafone Christmas party on December 3, 1992. At the time, he was a 22-year-old engineer.
The first text message simply said: "Merry Christmas."
What's it doing to the kidz???
Since that December, the informal language of the SMS and other digital platforms has become a social concern, especially for its effect on kids.
Will a generation emerge, raised on the smartphone, that can't tell "ur" from "your?"
Nenagh Kemp, a senior lecturer in psychology at the University of Tasmania, studied the effect of text messaging on grammar.
She tested 243 UK primary school, high school and university students to see if grammatical violations made when text messaging impacted their ability to know and use correct grammar in other circumstances.
Her 2014 research found little evidence that texting was tied to grammatical decline.
Instead, Dr Kemp suggested, people who are confident with spelling and grammar may be more expert in interpreting new ways of ways of writing, from the shortening of words to emoji.
"I think it's just another example of any kind of anxiety about technology, but this is very clearly a different way of writing," she said. "It is people adapting."
R U doing it wrong?
Adults may be anxious about the words children use in texts because it leaves them out. It hides meaning they cannot immediately interpret.
This is a common experience: most of us have probably pondered the hidden meaning of "so" versus "soooo". And emoji? That's even more complicated.
This tension exists because when we text, we miss social cues we might receive when speaking with someone in-person or by phone: tone, pauses or facial expressions, for example.
To make up for it, many of us use "textisms".
These are emotional embellishments - say, the emoji with love hearts for eyes, three exclamation points in a row or exaggerated spelling.
"A 'textism' is really any of those things that we add to a text message that lets us again capture some of the kinds of meaning that get lost when we're texting," said Celia Klin, a professor of psychology at New York's Binghamton University.
"Things that add meaning to the words that are beyond words themselves."
Even the most common punctuation can include social information, depending on the circumstances.
Professor Klin was part of a study that gave university students text messages that ended in a one-word response, with or without a full stop.
"Without a period, if it's one word or two words, it seems kind of neutral," she said. "Adding a period seems to add some sarcasm, abruptness - something negative."
Also, be wary of how you say "okay" in text messages.
"We did do one study looking at the word 'OK' versus 'K'," Professor Klin added. "And certainly, people thought just the letter 'K' was nasty and angry."
Ok got it!!! So what's nxt?
Language typically changes slowly, but within text speak, certain modes of communication have gone in and out of fashion at breakneck speed.
These days it's rare (and dorky) to see anyone under 25 saying "c u later" or "grt".
"If I ask university students if they use these abbreviations anymore they laugh and they go, 'oh my mum does, but I wouldn't'," Dr Kemp said.
While you still don't see much text speak in the newspaper, she suggested its influence would only grow beyond the confines of the messaging app. We cannot stop language's evolution.
"Most people have the sense that whatever language sounded like when we learned it was where evolution was supposed to have stopped," Professor Klin said.
"We don't speak like our great grandparents did and our great grandchildren won't speak like we did."
Some literary traditions may be left behind to gather dust in the dial-up era - Dr Kemp believes the apostrophe is not long for this world.
"I think that's something that maybe over the next 50 years or so may eventually die a death," she said.
As for Mr Papworth, the original texter, the significance of his message was not immediately clear.
But he is untroubled that his first text contained no special text speak. Not even "Merry Xmas."
"Maybe if I'd tried to be more philosophical, in 200 years' time, people would be trying to figure out what I was really thinking," he said.