A mnemonic phrase is a sequence of words used to represent cryptographic entropy in a human-readable form. In compatible wallet systems, the phrase can be converted into the initial key material from which wallet keys and addresses are derived.

In everyday usage, the terms seed phrase and mnemonic phrase are often treated as synonyms, although technical terminology can vary by standard. For example, BIP-39 defines a mnemonic sentence that encodes entropy and a checksum and can then be converted into a seed.

Relationship to HD wallets

After recovering the root seed, the wallet can use a derivation path to generate different branches of keys and addresses. As a result, one mnemonic phrase can correspond to many addresses and accounts.

A mnemonic phrase must be treated as secret key material. Exposure can allow recovery of the corresponding keys, while loss without another backup can result in permanent loss of access to assets.