"dimnames"(x)
"dimnames"(x) <- valueRGList, MAList, EList, EListRaw or (not for assignment) MArrayLMdimnames(x): see dimnamesNULL or a list of length 2.
If a list, its components are either NULL or a character vector the length of the appropriate dimension of x.
A consequence is that rownames and colnames will work as expected.
dimnames in the base package.
02.Classes gives an overview of data classes used in LIMMA.