In answers on this site often the word "u-substitution" appears. Why this is called u-substitution? Is it the same as integration by substitution?
(I never heard this term before and I'm not sure if we have it in my native language)
Edit: I myself find the question rather stupid. However, I constantly was thinking "maybe I'm missing something". From the comments I can see that I'm not the only one who gets confused if something simple like "integration by substitution" is called something else like "u-substitution". Especially, if there is "u-substitution" maybe there is "v-substitution" and "t-substitution", and ... . All things which I might never heard of.
So I guess I leave this question here for everybody else who does not know what u-substitution is.