A full stop on an old-fashioned typewriter was a large black blob as wide as a letter. When computers arrived they brought in typefaces with proportional spacing and the full stop diminished to a small dot.

For me, as a former typewriter user, the effect was to make the full stop matter less. The most crucial part of the sentence became a mere speck: easy to insert unthinkingly, easy to miss out altogether.

Then along came another threat - texting and chatting online. The dialogic visual language of texting speech bubbles, pinging left and right on your phone, has little use for full stops. A single-line text needs no punctuation to show that it has ended. In lieu of a full stop, we press “send”. The end of a text is now more commonly marked by a kiss, or an emoji, than a full stop. Studies have even shown that people tend to read a text that ends with a full stop as curt or passive-aggressive.

We live in a digital age that likes to pretend that writing is speech. We tap out emails, texts and update our social media profiles in the places – busy commuter trains, cafes and streets – where we also talk. We write as if we were talking. This kind of digital writing is often done quickly in the hope of an instant response. It is a slightly interrupted way of having a conversation.

 A good sentence moves smoothly and cleanly towards a stop. The best way to ensure this happens is to put the important stuff at the end

But writing is not really conversation. One of the purposes of writing effectively is to store and spread information in a form that does not require anyone else’s bodily presence while it is being written. A piece of writing is its own small island of sense, from which the writer has been airlifted and on which no one else need live.

So with any kind of formal or semi-formal writing we craft at work – even an email – the full stop and where we put it are crucial. A sentence should assume the reader’s existence but cannot, like a text speech bubble, keep demanding a response. With a full stop, your sentence becomes self-supporting.

The full stop offers the reader relief, allowing them to close the circle of meaning and take a mental breath. Full stops also give writing its rhythm. They come in different places, cutting off short and long groups of words, varying the cadences – those drops in pitch at the sentence’s end which signal that the sentence, and the sentiment, are done.

 

A good sentence moves smoothly and cleanly towards a stop. The best way to ensure this happens is to put the important stuff at the end. A sentence ordered like this feels more deliberate and more memorable just as, when you stop speaking, what sticks in your listener’s mind is the last thing you said. A sentence’s strongest stress falls on its last stressed syllable, just before the full stop. A sentence has a special snap if its last syllable is stressed: I binned that brainless book. A sentence with a strong end-stress says that its writer cared how its words fell on the reader’s ear.

If you want to write well, learn to love the full stop. See it as the goal towards which the words in your sentence adamantly move. The full stop is a satisfying little click that moves your writing along so the next sentence can pick up where it left off.

--

Joe Moran is Professor of English at Liverpool John Moores University and author of First You Write a Sentence: The Elements of Reading, Writing … and Life.

To comment on this story or anything else you have seen on BBC Capital, please head over to our Facebook  page or message us on Twitter.

If you liked this story, sign up for the weekly bbc.com features newsletter called "If You Only Read 6 Things This Week". A handpicked selection of stories from BBC Future, Culture, Capital and Travel, delivered to your inbox every Friday.