What packages require a given package?

How do you determine what packages require a given package?

repoquery --tree-whatrequires <package>

For example, let's say you want to find out what packages depend on rdma:

$ repoquery --tree-whatrequires rdma
rdma-1.0-14.el6.noarch [cmd line]
\_ opensm-3.3.9-1.el6.x86_64 [1: rdma = 1.0-14.el6]
$

There you have it... opensm is the only package that requires rdma.

Source: Stack Overflow