Heard in the high school hallway: #.

No, that’s not pronounced “pound” or “number.” Try “hashtag.”

The character so ubiquitous on the social media website Twitter, first as an organizing tool and then as a way to add commentary to short posts, has made the leap to everyday speech, especially among teens.

“In the last six months, it’s gotten really popular to speak in hashtags,” said Megan Skelly, a senior at Lakeville North High School in Minneapolis. “It’s kinda funny.”

For example?

“Let’s say somebody got mad at you for something you aren’t sorry for,” said Mikayla Lonergan, a Lakeville North sophomore. “Whatever. Hashtag, sorry not sorry.”

Her friends offer other examples: Quote something profound? “Hashtag, truth.” Flirting with that cute classmate? “Hashtag, I can’t date you if … (insert silly qualifier).”

Odd as it may sound, linguists say it’s nothing new.

“This is the kind of thing we do with language. We take things from one context and put it in another,” said Naomi Baron, author of Always On: Language in an Online and Mobile World and a professor at American University. “It’s a way of being cute.”

Acronyms from instant messaging and texting build off abbreviations from previous eras.

In a sense, RSVP and AWOL paved the way for OMG and BFF. In the case of LOL, the meaning has changed over time from “lots of love” to “laugh out loud.” It’s a small leap from there to speaking in hashtags.

While the shortened phrases, written or spoken, may start with a niche of the population, it doesn’t take long for them to spread in a digital age.

Baron points to colleagues in their 50s, 60s and 70s who toss out BRB (as in “be right back”).

“We do this because we’re social animals, as well as being people who should act our age,” Baron said. “You hear these things, why not use them?”

As hashtags become more commonly known, the trendiest make the jump to speech.

“You’d never really say one that isn’t popular, because then people wouldn’t get it,” said Kendall Huber, another Lakeville North sophomore.

It’s also possible to use hashtag lingo without uttering the word “hashtag” itself.

As in: “I can’t find a wireless connection … (pause) First-world prob(lem).”

Translation: Yes, I know I’m whining about an inconvenience in a generally well-off country.

Or turn the school’s unofficial motto into a hashtag both typed and spoken. If you’re a Lakeville North student full of school pride: “Let’s go to the football game! (#)North or none!”

Use the hashtag equivalent of air quotes — criss-cross the extended index and middle fingers of both hands while making a quip — at your own risk.

“I’ve only seen that a couple times,” Lonergan said.

Students in teacher Nicole Kronzer’s English classes at Champlin Park High School have made a good-natured game of stumping her with hashtag talk.

It started when she confessed confusion when a student quipped, “Hashtag, YOLO.” The acronym means “you only live once” and the laughing students told her it was “like so three months ago.”

“I think there’s absolutely no way an adult can keep up, and maybe we shouldn’t,” Kronzer said, admitting she’s impressed by the cleverness of the ever-changing lingo.

She often compares notes with her colleagues.

“Lunchtime becomes this teenage-to-adult dictionary translation time sometimes,” Kronzer said.

Entertained or annoyed, some can’t help but wonder what all this digital babble bodes for grammar, spelling and proper speech.

After all, a 2009 study by the Pew Internet & American Life Project found that half of teens let informal language slip into their school writing assignments. Thirty-eight percent admitted using shortcuts learned through instant messaging and email.

But University of Minnesota linguist Anatoly Liberman, who lumps Twitter and texting in with all sorts of other slang, is not concerned.

“It’s alive today and dead tomorrow,” he said. “It takes stronger artillery to destroy English.”