“Card sorting is a powerful technique for assessing how users group related concepts together. In its simplest form, a researcher would write concepts – usually menu items for interaction design – on cards and ask users to group related items together. In a closed card sort, the number of groups and their names are fixed. In open card sorts, the number and names of groups are determined by the participants, although the researcher may specify limits (3 to 5 groups, for example).” (William Hudson – Syntagm) – courtesy of cityofbits