WASHINGTON — OMG. Dat u mom?

Yes, it is. Parents are horning in on their teens' lives through text messaging. Sending shorthand cell phone messages used to be the province of the younger set — under the dinner table, in the car, at all hours of the night.

Now parents responding with their own quick dispatches — "RU there," "Running L8" — are part of the fastest-growing demographic in text messaging, which is one of the biggest areas of the mobile-phone industry.

Parents frequently follow their children into technology, setting up pages on the MySpace and Facebook social-networking sites, for example, to be part of their child's network of online friends.

Adult text messaging is outstripping the growth rate among the youngsters. In the past two years, use of the technology by those ages 45 to 54 increased 130 percent, according to M:Metrics, a market-research firm. By comparison, those ages 13 to 17 increased their text messaging by far less, 41 percent.

Sprint Nextel said teens and ages 40 to 50 were the most active text-message users from June 2006 to June 2007. Among adults, mothers are driving the growth the most, the company said. Overall revenue from data services on cell phones, including text messages, surged 53 percent last year to $23 billion, according to CTIA, the wireless-industry trade group.

"Parents like the immediacy of it and that it is not intrusive. ... It's become an important way of communicating with their kids," said Ralph de la Vega, chief executive of AT&T Mobility, the nation's largest wireless carrier.

In a 2006 study commissioned by AT&T, 50 percent of adults who text-messaged said they started because of their children.

Suzanne Furman, of Rockville, Md., had watched her teenage son, Jesse, move his thumbs at lightning speed over the keypad, sending hundreds of messages a month to friends.

"It didn't take me long to realize I'd have to learn how to text if I wanted to keep up with him," Furman said.

So she did — with some prodding.

Two years ago, Jesse sent a message asking when she would come to pick him up from an outing with friend.

"I just stood there frozen and realized I had to figure out how to reply," said Furman, who is an avid user of similar technologies, such as the Web and digital music. She thumbed through the numeric keyboard on her Motorola KRZR phone, taking several minutes to write, "Coming now."

With that, Furman dove into a technology she says is still difficult to master but has become a staple for family communication. She now texts her husband to coordinate such chores as dry-cleaning pickups and sports practice drop-offs.

'PERFECT FOR MOMS'

Schools have caught on. Fairfax County, Va., and Montgomery County, Md. — two of the Washington area's largest districts — send automatic text-message alerts for weather-related school closures and other emergencies. www.RainedOut.com sends message alerts on soccer practice cancellations in Washington area leagues.

"Text messaging is perfect for moms because it doesn't require a BlackBerry or high-end data device, but can be used on any phone," said Roger Entner, a senior vice president at IAG Research.

He added that working parents also use text messaging while at work to check in with their children.

For families, wireless carriers' flat-rate plans have been a panacea for sky-high texting bills, in some cases incurred by a teen sending hundreds or thousands of text messages a month.

After that happened to Lynda Johnson, she switched her family to Sprint's flat monthly plan. Her 17-year-old daughter and 20-year-old son were sending hundreds of text messages monthly. Now the Silver Spring, Md., mother tallies up her own text messages.

Her daughter, Jesse, was given a cell phone at age 14 for emergencies and for coordinating logistics with her parents. More often, however, Jesse would spend hours texting friends from the couch or back seat of the car.

When Johnson called her daughter, she said, "I could tell I was bothering her or interrupting because her voice was cold and hurried."

So one evening, while Jesse was at a sleepover, Johnson sent her first text message: "Sweet dreams. Luv u." It was a way to check in with her 14-year-old without seeming overbearing.

"I don't want to interrupt her with her friends but also want her to know that I'm here for her."

FINDING SHORTCUTS

Bethesda, Md., mother Evon Ruffin had to learn a new language as well as the new technology. Cryptic abbreviations like OMG, for "Oh, my God." And L8R for "later."

Carriers have tried to aid adults new to texting. AT&T, for example, offers a four-page guide on lingo. Verizon Wireless's Quick Text feature allows users to choose from a menu of phrases like "What's up?" and "On my way," so they don't have to type each letter.

Ruffin said she draws her own limits on joining the text-message culture. Not so her husband, who recently sent her wife a one-letter text that read "k" for "OK."

"Come on now, 'OK' is already abbreviated," she protested. "And you're going to try to shorten it even more? Please."