Rank-metric codes

This is a chapter of the upcoming "A Concise Encyclopedia of Coding Theory", W.C. Huffman, J.-L. Kim, and P. Sole' Eds., CRC Press. The chapter gives an introduction to the mathematical theory of rank-metric codes. Treated topics include: definition of rank metric, equivalence of codes, support of a codeword and of a code, duality, weight enumerators and MacWilliams identities, higher rank weights, MRD codes, optimal anticodes, and q-polymatroids associated to a rank-metric code.