Another form of collation is radical-and-stroke sorting, used for non-alphabetic writing systems such as Chinese hanzi and Japanese kanji, whose thousands of symbols defy ordering by convention. In this system, common components of characters are identified; these are called radicals in Chinese and logographic systems derived from Chinese. Characters are then grouped by their primary radical, then ordered by number of pen strokes within radicals. When there is no obvious radical or more than one radical, convention governs which is used for collation. For example, the Chinese character for "mother" (妈) is sorted as a six-stroke character under the three-stroke primary radical (女).
The radical-and-stroke system is cumbersome compared to an alphabetical system in which there are a few characters, all unambiguous. The choice of which components of a logograph comprise separate radicals and which radical is primary is not clear-cut. As a result, logographic languages often supplement radical-and-stroke ordering with alphabetic sorting of a phonetic conversion of the logographs. For example, the kanji word ''Tōkyō (東京), the Japanese name of Tokyo can be sorted as if it were spelled out in the Japanese characters of the hiragana syllabary as "to-u-ki-yo-u" (とうきょう), using the conventional sorting order for these characters.
In addition, in Greater China, surname stroke ordering is a convention in some official documents where peoples' names are listed without hierarchy.
The radical-and-stroke system, or some similar pattern-matching and stroke-counting method, was traditionally the only practical method for constructing dictionaries that someone could use to look up a logograph whose pronunciation was unknown. With the advent of computers, dictionary programs are now available that allow one to draw a character using a mouse or stylus.
Read more about this topic: Collating Sequence