The word preferential is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 20
Highest Scoring Words With Friends™ Play In The Letters preferential
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Seven Letter Word Alert: (80 words)
alerter, arenite, earlier, enteral, enterer, eternal, fainter, feltpen, ferrite, fertile, fireant, firepan, fleapit, fleeter, flirter, frailer, inepter, inerter, inflate, latrine, leafier, learner, leerier, lineate, painter, partner, peatier, penlite, pentail, perlite, pertain, plainer, planter, praline, preener, prefile, prefire, prelate, preteen, printer, ratline, realter, reefier, reenter, refiner, reflate, refrain, reinter, relater, relearn, reliant, repaint, repanel, repiner, replait, replane, replant, replate, repleat, replete, replier, reprint, reptile, retinal, retiree, retrain, retrial, taperer, tearier, teenier, terpene, terpine, terrain, terrane, trailer, trainee, trainer, trenail, triaene, trifler