BIP39 Words Starting with U (35 words)

The 35 BIP39 words that start with U run from #1889 ugly to #1923 utility in the English wordlist: indexes 1888 to 1922, or 11101100000 to 11110000010 in binary. That is 1.7% of the 2048 words, the 20th-largest of the 25 letter groups. Word length goes from 3 letters (use) to 8 (umbrella and universe).

Six three-letter beginnings are shared by two or more words; the largest, with 4 words each, are "uni" and "use". The 16 words in these groups need their first four letters to be told apart, while 16 are identified by the first three, and 3 (ugly, umbrella and utility) by the first two. The short word use also begins longer ones, so a four-letter backup keeps it whole.

Four of the 35 words have look-alikes one letter away, such as use and used. Read aloud, 14 pairs differ by a single sound, for example under and undo. Two spellings are shared with the French BIP39 list, at different indexes: unique and usage. Five of the words appear in the official BIP39 test vectors, among them uncle and unfold.