internal conversion

19 LETTERS · STARTS WITH I

internal conversion is a valid 19-letter word worth 23 points in Scrabble and 30 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

I1N1T1E1R1N1A1L1C3O1N1V4E1R1S1I1O1N1

1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 0 + 3 + 1 + 1 + 4 + 1 + 1 + 1 + 1 + 1 + 1 =23 PTS

DOUBLE WORD → 46TRIPLE WORD → 69

MEANING

What does internal conversion mean?