echo

"echo" is the #560 word in the official BIP39 English mnemonic wordlist. It is encoded as the 11-bit binary value 01000101111 (decimal index 559), placing it at the 27% mark of the full 2048-word list.

The 4-letter prefix "echo" uniquely identifies this word among all 2048 entries. At just 4 characters, "echo" is one of the shorter words in the BIP39 list, making it quicker to type during wallet recovery but potentially easier to confuse with similar short entries.

Located in the middle section of the wordlist (index 559), "echo" belongs to the "E" letter group, which contains 100 words. It is the #9 entry in that group. Mid-range words have a balanced mix of 0s and 1s in their binary representation.

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