A spore is a tiny single cell that some living things make in order to reproduce — mushrooms and other fungi, ferns, mosses, and many bacteria. It works a bit like a seed: it travels, lands somewhere, and grows into a new organism. But biologists are careful here, and so should we be: a seed is a small packed-up plant with a food supply around it, while a spore is usually just one cell with a tough coat and no food store. Spores are usually far smaller — you cannot see one on its own; the brown dust that falls from a mushroom, or the rusty powder on the back of a fern leaf, is millions of them together. Two extra things worth knowing. Spores are famously tough: some bacteria turn themselves into spores to survive heat, dryness, and years of waiting, and they wake up when conditions improve. That is why 'spore' turns up in food safety and hospital writing, where the point is that ordinary cleaning does not kill them. And people use it loosely outside biology, especially in stories and games, for anything that drifts, lands, and spreads — 'the idea spread like spores'. There is also a verb, 'to spore', meaning to produce spores, but it is technical and uncommon; most writing says 'release spores' instead. The noun is countable: one spore, many spores.