Any result of human labor that is produced in order to be exchanged on the market.
Origin of the commodity
Not every product of human labor is a commodity. In fact, until very recently most production was not carried out for the market. Not even the first Neolithic exchanges can be considered commodity trade. As far as we know, the original experiences of exchange took the form of more or less symbolic and ritualized donations of reciprocal gifts between communities. The goods and services exchanged did not establish an exchange value between them, were not meant to be equivalent and were therefore not commodities.
During the development of slavery as a mode of production, commodity exchange expanded for the first time, without becoming the main aim of social production. After all, the main productive force, slave labor, was a commodity only in a very limited sense.
The feudalism that followed was not a commodity system either, and in fact the minting of coins was practically non-existent in Europe from the eighth to the tenth centuries and very scarce until the twelfth. Feudal serfs can be considered commodity producers only very marginally and belatedly: most of their labor produced useful objects for their own consumption or that of their lords, which were not intended for exchange nor measured by an exchange value. Not even the labor power of the peasant and the land he worked could be sold or exchanged for other commodities or for money.
Capitalism is the first mode of production that requires the commodification of all products and social relations. Its spread has turned the commodity into the universal form of labor and its products, and in doing so it has cloaked social relations in the false egalitarianism of exchange between equivalents, presenting relations between people as relations between things: the famous commodity fetishism.