Commodity
Etymology
From Latin commoditas, "convenience, fitness, advantage" (from commodus, "suitable" — com-, "with," plus modus, "measure"). It first meant something useful or advantageous, then narrowed to an article of trade, and finally to raw goods traded in bulk by grade rather than by brand.
noun · /kuh-MOD-ih-tee/
A basic, interchangeable good — like oil, wheat, or copper — where one unit is essentially the same as another regardless of who produced it.
What it names
It explains why some products compete only on price: when buyers cannot tell one seller’s version from another’s, there is nothing to compete on but cost.
Example
Once bottled water became a commodity, brands fought mainly on price and packaging.
Related idea
A commodity’s sameness is why volatility in its price hits everyone at once — buyers cannot switch to a "better" version to escape it.