Morpheme
A morpheme was the smallest linguistic unit within a word that could carry a meaning.

In 3189, after Ensign Sylvia Tilly suggested a dark matter interface for the spore drive, Lieutenant Commander Paul Stamets informed her that dark matter was comprised of subatomic particles and the mycelial network was a subspace domain. He then added,  "The prefix 'sub' being the only morpheme that remotely connects those two ideas." ()

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Linguistics