Today, I was reading an article on pharmaceutical companies making minute changes to a drug in order to extend the patent. In one instance, the company profiled did not actually change the content of the drug, just the outward appearance. This got me thinking, is there a word in the English language that means “to change without changing” or “a change so small that it’s not a change at all”? I thought about the word superficial, but that doesn’t seem to fit.
English doesn't get much more precise than this...
Infinitesimal — immeasurably or incalculably minute.
It gets a bit mind-boggling when infinitesimal amounts are involved in, for example, homeopathic remedies that are so diluted there's only a very low probability of even a single molecule of the original substance being present. Which to me means an amount so small it's not actually there.
EDIT: I can't resist pointing out this answer itself now embodies an (almost) infinitesimal change. It was recently amended (not by me) to add a space before the first word. But you don't see it because of how the ELU display works (I only twigged by looking at the edit source).
A phrase I might use is a negligible change, which is often used in the Sciences to mean a change small enough to be ignored.
However, in the context of Science, a negligible change can be noticeable - it's just so small that it won't affect the system or experiment. Therefore, this might not be the word you're looking for.
Imperceptible is very close although it can speak more to the perception of the viewer of the change more than the change itself.
I have not found a good word or succinct phrase for this; I think de minimis is the best that I have come across. Sure it's Latin, but it's either in the lexicon of most educated persons or they could quickly discern the meaning upon hearing it or reading it.
I have seen this term used in written communication to express the concept in the OP, but only in legal opinions and legal scholarship--e.g., "de minimis infringement" refers to an activity that satisfies the technical strictures of infringement, but the level of the activity is so small that it would be practically absurd/unreasonable to punish that activity as infringement.
I suggest quantum change. I know that in general discourse the term is used to mean a change of huge significance but, as far as I understand it, that betrays its scientific origin. I stand ready to be corrected by those who know more about these things than I do, but in physics, isn’t a quantum the smallest amount of anything that can exist?
I think you're talking about a change that changes only the outward appearance of something. I like waiwai's cosmetic, but I think I would go for superficial as you mention in your question. I disagree that it is inappropriate.
a : concerned only with the obvious or apparent : shallow
b : seen on the surface : external
c : presenting only an appearance without substance or significance
(c) is particularly apt for the circumstance you describe.
I am not a native english speaker so I might get it wrong, but I sens a contradiction in the sentence
a change so small that it's not a change at all
Either it's a change or not. For what I understand, only in quantum mecanics things can and cannot be at the same time. See Schrödinger's cat
To address the action of the change as opposed to the quantity (addressed by previous answers), I would submit the colloquialism "to tweak" as a candidate for indicating a minor or indiscernible change.
Also, from hacker jargon comes the term "frob", or "frobnicate": http://outpost9.com/reference/jargon/jargon_21.html#TAG697
A change so small that it’s not a change at all is a nominal change.
X plus two minus two yields nominal results; no real change here but something did happen.
nom·i·nal /ˈnämən(ə)l/ adjective -Google
(of a role or status) existing in name only.
(of a quantity or dimension, especially of manufactured articles) stated or expressed but not necessarily corresponding exactly to the real value.