A radical is an ideograph or a component of an ideograph that is used for indexing dictionaries and word lists, and as the basis for creating new ideographs. The 214 radicals of the KangXi dictionary are universally recognised.

The examples enlarged on the slide show the ideographic character meaning ‘word’, ‘say’ or ‘speak’ (bottom left), and three more characters that use this as a radical on their left hand side.