As an adjective, concrete describes something real and solid that you can see or touch, or a specific example rather than a general idea. As a noun, concrete is a hard building material made from cement, sand, gravel, and water.
From Latin 'concrētus', meaning 'grown together, hardened', from 'concrescere' ('to grow together'). The building material sense comes from the idea of particles growing together into a solid mass.
We talk about 'concrete examples' because they feel as solid in your mind as a block of building concrete under your feet. Learning often fails when ideas stay too abstract; turning them into concrete images or cases makes them stick.
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