mu and um tie for the highest Scrabble score from um at 4 points. The top 2 of 2 words are shown here, with the full list organized by length below.
There are 2 two-letter words hiding in um: one comes from rearranging its letters, and um itself is already a playable word with no unscrambling required. If a familiar word is all you need, start with um. For points, the strongest plays are mu and um — each worth 4 points in Scrabble.
The full list follows, sorted A to Z; every score reflects tile constraints and skips board bonuses.
um is in the NWL, the official Scrabble word list for North America, and in the Words With Friends dictionary, so it's playable exactly as it stands and needs no unscrambling.
The 2-point gap between the two totals comes from the tile values themselves: Scrabble and Words With Friends price the same letters differently.
um is one of two two-letter words the same letters produce. No arrangement of the same tiles scores higher in Scrabble, so playing um unchanged also takes the maximum points these letters offer.
The highest-scoring plays from these letters are mu and um, worth 4 points in Scrabble, and nothing else built from um earns more points in Scrabble. Words With Friends prices the same letters differently, so the top of the list changes on a Words With Friends board. Both scores count tile values only and exclude premium squares.
The letters in um produce 2 valid words in the Scrabble and Words With Friends dictionaries. The word count by length is: 2 two-letter words.