unhappy

"unhappy" is the #1899 word in the official BIP39 English mnemonic wordlist. It is encoded as the 11-bit binary value 11101101010 (decimal index 1898), placing it at the 93% mark of the full 2048-word list.

The 4-letter prefix "unha" uniquely identifies this word among all 2048 entries. With 7 characters, "unhappy" is among the longer entries in the list, which reduces the chance of confusion with other words during manual seed phrase entry.

Near the end of the wordlist (index 1898), "unhappy" is part of the "U" letter group with 35 entries total, positioned at #11 in that group. Words in the upper range of the list have binary representations with more leading 1s.

In a 12-word seed phrase, each word encodes 11 bits of entropy. The probability of "unhappy" appearing in any specific position of a randomly generated phrase is 1 in 2048 (≈ 0.049%). A complete 24-word phrase encodes 256 bits of entropy, providing security equivalent to a key space of approximately 1.16 × 10⁷⁷ — far beyond the reach of brute-force attacks.