This week, the game developer Zynga is rolling out a refreshed version of Words With Friends, billed as the world’s most popular mobile word game. The new-and-improved Words With Friends 2 boasts various bells and whistles, like the “Solo Challenge” where you square off against bots, and “Lightning Rounds” that pit teams against each other. But a more profound change is going on invisibly: a huge expansion in the number of playable words.

To celebrate the eighth anniversary of the game, Zynga announced in September that it was adding 50,000 new words to what it calls the “Social Dictionary,” incorporating frequently requested items, as well as words inspired by pop culture and online communication. That includes not only contemporary slang like bae, yas, werk, turnt, and bestie, but also, more surprisingly, a handful of abbreviations like BFF (best friends forever), FOMO (fear of missing out), and TFW (that feeling when...).

While trendy initialisms might make for good marketing material, purists raised on Scrabble might balk at the additions. Doesn’t including these abbreviations go against the spirit of games like Words With Friends that have Scrabble burned into their DNA? (And no, Zynga isn’t making DNA playable, at least not yet.)

As the granddaddy of word-tile board games, Scrabble has long made clear what does and doesn’t count as a playable word. As Stefan Fatsis, the author of the book Word Freak about the competitive Scrabble world, has noted, when the game was first marketed in 1948, the rules were spelled out right inside the box: “Any words found in a standard dictionary are permitted except those capitalized, those designated as foreign words, abbreviations, and words requiring apostrophes or hyphens.”

The Official Scrabble Players Dictionary, first published in 1978, has followed those instructions to the letter. And when an open-source alternative to the Scrabble dictionary called ENABLE (an acronym for Enhanced North American Benchmark Lexicon) was released in 1997, it too considered abbreviations verboten. ENABLE, free from the proprietary burdens imposed by Scrabble’s trademark holders (Hasbro in the U.S. and Canada, and Mattel elsewhere), became a popular word list for game-makers developing their own Scrabble spinoffs, including, in 2009, a little game called Words With Friends.

The 174,000 words on the ENABLE list have served Words With Friends well over its eight-year history, ever since its first development by Newtoy (which was bought out by Zynga in 2010). While Words With Friends has enough differences from Scrabble, such as the distribution of letters and point values, to keep them from being sued by Hasbro and Mattel, the “no abbreviation” rule has been one point of agreement shared by the two games—until now.

According to Gurpreet Singh, the product director of Words With Friends, the new Social Dictionary is one way that the game is responding to player feedback. Every day, Zynga fields more than 5,000 suggestions for new words to make playable, and many of these have gone into the dictionary expansion. Interestingly, though, the Words With Friends suggestion form warns that they’re unable to add words from the traditional no-go categories: proper nouns, words with hyphens or apostrophes … and abbreviations.

So how did BFF, FOMO, and TFW make the cut among the 50,000 new words? When the Social Dictionary was being created, there was no attempt to include all abbreviations. “There are no hard and fast rules,” Singh told me—and when it comes to abbreviations, “Where do you stop?”

For now, there’s just a limited number of abbreviations included in the Social Dictionary, but Singh kept the door open to adding more. (Sorry, you can’t play OMG, LOL, WTF, BTW, or FYI just yet.) “We’re learning and evolving from talking to our players,” Singh said. “We want to make sure our player base is excited by these words. That’s our barometer.”

Singh also acknowledged that the game developers are “not aiming to be most correct from a dictionary perspective.” This is another way that Zynga has set Words With Friends apart from the more lexically straitlaced Scrabble. As the name suggests, the game is supposed to be a social experience that you enjoy “with friends,” so why shouldn’t the limits of acceptable words be more free and easy?

Despite this openminded attitude, it might be worth imposing a bit more consistency on the game’s new lexicon. If BFF is acceptable, and it’s treated as a noun, then surely the plural BFFs should be playable too. Inflections are generally a stumbling point for the Social Dictionary words: You now can play bae but not baes, bestie but not besties, swole (meaning “extremely muscular”) but not swoler or swolest. And you can’t really know if a word is currently playable unless you search for it in the game’s built-in dictionary or try playing it on the board.

That would be more of an issue if Words With Friends had real aspirations to be a competitive game with serious tournaments, like Scrabble. In fact, Words With Friends has occasionally organized competitions: In 2015, it held the Wordie Games, which attracted some top Scrabble players, including Conrad Bassett-Bouchard, who the year before had become the youngest-ever American Scrabble champion at the age of 24.

I checked in with Bassett-Bouchard, who is now an interaction designer for Google, and he said he has no trouble with Words With Friends crossing the line and adding popular abbreviations to its lexicon. “Its brand image has always been that it’s not so much about the dictionary,” he said. “It’s a totally different game from Scrabble, even if it happens to involve unscrambling words and putting them on a board. If you remove that Scrabble bias, there’s no reason why these abbreviations shouldn’t be acceptable.”