Re: Why do people use the expression 'chemistry' when describing relationships

Using "chemistry" to describe an interpersonal relationship is a very old rather than new usage of the word. The OED (Oxford English Dictionary) gives this definition for "chemistry": "an instinctual, apparently unanalysable, attraction or affinity between people or groups of people; the combination of personal characteristics that creates this." This sense of the word was first used in the 16th Century, and was presumably a figurative, if not poetic, interpretation of the original definitions of "chemistry", also from the OED: "Alchemy" or "the practice of medicine after the Paracelsian, as opposed to Galenic, methods." Thus, in the original sense of interpersonal "chemistry", this is a reference to an attraction or compatability that could otherwise be attributable to some potion or elixir that would have been administered by an alchemist or Paracelsian Doctor. As 20th Century science has examined the innumerable factors that contribute to interpersonal relationships, this definition has changed slightly in tone - it is now known that successful relationships are due to personal characteristics and not potions - however it is still used in a purely figurative sense, contrary to hundreds of years of failed attempts to find just such an elixir.