Image caption Even in French, the web employs a "cyber-utopian California-style libertarian discourse"

The informal version of "you" in the French language - "tu" - seems to be taking over on social media, at the expense of the formal "vous". As in many countries, online modes of address in French are more relaxed than in face-to-face encounters. But will this have a permanent effect on the French language?

Anthony Besson calls most people "vous". As a young man, it is a sign of respect to those older than him, and he's often meeting new people through his work in PR in Paris.

Yet this all changes on social media. "I always use 'tu' on Twitter," Besson says. "And not just because it takes up fewer of the 140 characters!"

Lots of other French people do exactly the same.

"Tu" is normally for family and friends, but when you're communicating through @ symbols, joining networks and tweeting under a pseudonym, a formal "vous" can seem out of place, even to someone you've never met.

Antonio Casilli, professor of Digital Humanities at Telecom ParisTech engineering school, says the web has been used as a tool for breaking down social barriers from its very beginning, resulting in a distinctively "egalitarian political discourse".

In the philosophy of the internet, we are among peers, equal, without social distinction, whatever your age, gender, income or status in real life Anthony Besson

The pervasive pattern of speech on the web in the 1990s, he says, was "cyber-utopian California-style libertarian discourse, inherited from 1960s counter-culture".

And the egalitarian spirit remained when the "participatory web" came of age in the mid-2000s, he suggests.

Social networking sites such as Twitter take this one step further, adopting codes "characterised by a heightened sense of emotional proximity", such as friending on Facebook, he says.

Twitter, meanwhile, follows on from a long line of internet forums where users could be anonymous.

"In the philosophy of the internet, we are among peers, equal, without social distinction, whatever your age, gender, income or status in real life," Besson says.

Addressing someone as "vous" - or expecting to be addressed as "vous" - on the other hand, implies hierarchy.

It is, as Casilli puts it, "a major break in the code of communication… an attempt to reaffirm asymmetric social roles… a manifestation of distance that compromises social cohesion".

Forget this at your peril.

Last year, Laurent Joffrin, director of left-leaning news magazine Nouvel Observateur, turned on a follower, asking who authorised him to use "tu" - "Qui vous autorise a me tutoyer?" (Joffrin, of course, used "vous".)

A storm erupted. Joffrin the accuser was himself accused of being rude and condescending.

People on Twitter would never dare to go up to someone in the street and call them 'tu' because it's a form of violence Laurent Joffrin

"The fact that he was a public figure who was part of an elite probably didn't help as he expected some respect and viewed 'tu' as an insult," Besson says.

He likens knowledge of the online social codes to a form of cultural capital - you either have it or you don't. And while younger people may be more likely to have it, there is no guarantee.

"Just because you're young doesn't mean you're better at using the internet than your grandmother," Besson says.

A year later, Joffrin has stopped using Twitter - his last tweet was in October - though he says this is nothing to do with the "tu" drama.

"It was unpleasant," he says of that episode. "There's a group of people who think they are superior because they know a way of talking [on Twitter] that others don't. I don't like the hierarchy. They want to impose their codes.

"It doesn't bring people together, it heightens tensions. It's an appalling culture. People on Twitter would never dare to go up to someone in the street and call them 'tu' because it's a form of violence - you see drivers insulting each other using 'tu'.

In other languages In German there's a tendency to use the informal "du" rather than the formal "Sie" on social media

there's a tendency to use the informal "du" rather than the formal "Sie" on social media In Russian the formal "vy" remains standard between strangers online

the formal "vy" remains standard between strangers online Language is liable to be even more formal than in face-to-face contact on the Japanese social networking site, Mixi

social networking site, Mixi The informal "to" is more common than the formal "shoma" on social networks in Persian

The formal "nin" is rarely used in Chinese anyway but online language is often very informal and has generated a new lexicon of web slang

anyway but online language is often very informal and has generated a new lexicon of web slang In the UK emails are now far more likely to begin with "Hi" than letters were in the era of snail mail

"In big cities especially, you need respect and courtesy. And on Twitter, there isn't respect."

In Spain, the same thing is happening to modes of address online. The familiar "tu" dominates, with the formal "usted" a rarity.

As in France, the normal style of writing on Twitter in Spanish is "informal, direct and very personal", says Prof Jose Luis Orihuela of Navarra University, author of a book called Mundo Twitter (Twitter World).

Melchor Miralles Sangro, host of the Cada manana morning programme on ABC Punto Radio in Spain, who has more than 50,000 followers on Twitter says he usually uses "tu" online but is quite relaxed about forms of address. "I don't mind which form of 'you' people use to address me," he says. "I have no problem with either."

In Italian, meanwhile, the move towards "tu" was under way long before the arrival of the internet and social media. They merely reinforce an existing trend.

"In Italian, even among strangers or among people belonging to different generations, the informal 'tu' is much more frequent than the formal 'lei'," Casilli says.

"The shift in the use of informal language online is… less dramatic than in French."

If people's first contact is on social media and they start using 'tu', it would be awkward to use 'vous' in a different context Prof Bert Peeters, Macquarie University, Australia

It's too early to say whether Twitter will change how French people talk in everyday life.

Historically, the biggest shifts towards "tu" occurred at the time of the French Revolution and during the social upheavals of May 1968.

"People who played an active role in May '68 pleaded in favour of getting rid of the distance created by 'vous' and doing away with hierarchy," says Prof Bert Peeters, of the French and Francophone Studies department at Macquarie University in Australia, co-editor, of Tu ou vous: l'embarras du choix - Tu or vous: an awkward choice.

"However, as they grew up and became mature adults, they realised that having just 'tu' in French was not adequate, or not part of being French, and 'vous' started coming back."

Although "tu" is more common than it was pre-68, strict rules still govern its use.

"You would offend a lot of people if you used 'tu' and they didn't know you. It is difficult to say whether social media will change this," Peeters says.

"However, if people's first contact is on social media and they start using 'tu', it would be awkward to use 'vous' in a different context. Once you start with 'tu', it is very hard and very rare to abandon it."