BIP39 Words Starting with O (55 words)

The 55 BIP39 words that start with O run from #1215 oak to #1269 ozone in the English wordlist: indexes 1214 to 1268, or 10010111110 to 10011110100 in binary. That is 2.7% of the 2048 words, the 17th-largest of the 25 letter groups. Word length goes from 3 letters (oak, off and 4 more) to 8 (ordinary and original).

Nine three-letter beginnings are shared by two or more words; the largest is "out", with 4 words. The 21 words in these groups need their first four letters to be told apart, while 24 are identified by the first three, and 10 (oak, odor, oil and 7 more) by the first two. The short words off and own also begin longer ones, so a four-letter backup keeps them whole.

13 of the 55 words have look-alikes one letter away, such as once and one. Swapping two neighbouring letters turns odor into door. Read aloud, 43 pairs differ by a single sound, for example oak and okay. Three spellings are shared with the French BIP39 list, at different indexes: opinion, orange and ozone. Five of the words appear in the official BIP39 test vectors, among them office and open.