brain

"brain" is the #216 word in the official BIP39 English mnemonic wordlist. It is encoded as the 11-bit binary value 00011010111 (decimal index 215), placing it at the 11% mark of the full 2048-word list.

The 4-letter prefix "brai" uniquely identifies this word among all 2048 entries. At 5 characters, it falls in the typical length range for BIP39 words, balancing readability with distinctiveness during manual wallet recovery.

Positioned in the first quarter of the wordlist (index 215), "brain" starts with "B" — a letter group containing 117 words total. It is word #80 within that group. Words early in the list have lower binary values with more leading zeros, which can be relevant when analyzing raw entropy data.

In a 12-word seed phrase, each word encodes 11 bits of entropy. The probability of "brain" 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.