TITLE: A question on non noetherian ring
QUESTION [6 upvotes]: Let $R$ be a reduced commutative non noetherian ring of dimension $d$  and $a$ a non zero divisor. Can I say that Krull dimension of $R/(a)$ is at most $d - 1$?

REPLY [5 votes]: Since $a$ is a non-zerodivisor of $R$, it does not lie in any of the minimal primes of $R$.  Therefore any chain of primes in $R$ that all contain $(a)$ has no minimal prime in the chain and can therefore be extended to a larger chain of primes in $R$, namely, by including a prime properly contained in the smallest prime in the chain.  So $\dim R/(a) < \dim R$.