mnemonic

1. N-COUNT A mnemonic is a word, short poem, or sentence that is intended to help you remember things such as scientific rules or spelling rules. For example, "i before e, except after c" is a mnemonic to help people remember how to spell words like "believe" and "receive." 助记符号; 助记口诀[oft N n]

...mnemonic devices. ...助记工具。