# Baby/Papa/Mama/Big Rudin

Recently, I was looking for the reviews of some Analysis books while encountered terms such as Baby/Papa/Mama/Big Rudin. Firstly, I thought that these are the names of a book! But it turned out that these are some nick names used for the books of Walter Rudin. So I was thinking that

$1$. What are the corresponding books of these nick names?
$2$. Why such nick names are chosen? or What are their origins?

• Baby Rudin is Principles of Mathematical Analysis; I’m pretty sure that I was already hearing that name back in the early $1970$s when I was his wife’s student. Big Rudin is Real and Complex Analysis. Baby Rudin is an (advanced) undergraduate text; Big Rudin is a graduate text. Jul 18 '16 at 19:39
• "Baby Rudin" is Principles of Mathematical Analysis, so called because it's the most elementary of his books and and its topics are prerequisites to the others. $\qquad$ Jul 18 '16 at 19:39
• Baby = Principles of Mathematical Analysis; Papa = Real and Complex Analysis; Grandpa = Functional Analysis Jul 18 '16 at 19:40
• @H.R.: I assume that Papa Rudin is, as Kaj said, the same as Big Rudin, though I don’t think that I’ve actually noticed the name before; I’ve never encountered the name Mama Rudin. (That ought to be Mary Ellen, his wife — except that she didn’t write any books!) Jul 18 '16 at 19:47
• @David: Borderline; I chose not to count it, but it wouldn’t be wholly unreasonable to count it. (I definitely didn’t forget it: I proofread the ms. and suggested a few small changes.) Jul 18 '16 at 20:10

$1$. Baby = Principles of Mathematical Analysis;
$2$. Papa/Big = Real and Complex Analysis;
$3$. Grandpa = Functional Analysis;
and it seems that the difficulty of contents of the books grows with the age of the nick names! Firstly, you are a baby and things are easy to handle. Then you grow up and become a papa and things get more complicated. Finally, when you are a grandpa you should take care of your legacy very carefully which needs a hardwork! So $1$ is a prerequisite of $2$ and $2$ is prerequisite of $3$.