Reading and writing involve print-related and meaning-making processes, which draw on numerous skills and knowledge. The contributing skills and knowledge, and reading and writing have: a) hierarchical relations where lower order skills support higher order skills in a systematic and cascaded way; b) interactive relations where reading and writing skills, and their contributing skills develop interactively, influencing each other, mediated by learning experience and practice; c) reading and writing difficulties co-occur; and d) dynamic relations where reading-writing relations change depending on the development of word reading and spelling skills, grain size of reading and writing, and tasks and measurement. [This chapter was published in: "International Encyclopedia of Education, vol. 6," edited by R. J. Tierney et al., Elsevier, 2023, pp. 335-343.]