Elves and Fays

Elves noun - An acronym for emissions of light and very low frequency perturbations due to electromagnetic pulse sources; extremely bright extremely short (less than a msec) electrical flashes forming a huge ring (up to 400 km diameter) in the ionosphere.

Fays and elves are semantically related. In some cases you can use "Fays" instead a noun "Elves".

Elves and fays are semantically related. You can use "Elves" instead a noun "Fays".