Elves and Pygmies

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.

Pygmies and elves are semantically related. In some cases you can replace term "Pygmies" with "Elves", this nouns are similar.

Elves and pygmies are semantically related. You can use "Elves" instead a noun "Pygmies".