a device such as a pattern of letters, ideas, or associations that assists in remembering something, for example Richard Of York Gave Battle In Vain for the colours of the spectrum (red, orange, yellow, green, blue, indigo, violet)

I had to invent a mnemonic, in other words a prompt, that I could use in chemistry exams

aiding or designed to aid the memory

in terms of leadership, I use the mnemonic device OATE: ownership, accountability, transparency, and empowerment