COTS
Beginner
Ordinary parts that anyone can buy, like the chips in phones and laptops.
Novice
Commercial off-the-shelf: ordinary parts made for the mass market, not designed or tested for radiation.
Expert
Better performance, power and cost than radiation-hardened parts, but highly susceptible to radiation. Small satellites often use them surrounded by hardened supervisors, error correction, watchdogs and scrubbing.
Explained in Space (Industries).