What Is It?
Classification involves grouping items into one or more categories based on certain distinguishing characteristics. The categories are thoughtfully labeled so that the labels become descriptors for the members of the category.
Why Is It Important?
Classification demonstrates understanding of the relationships among things and helps to clarify concepts. For these reasons, classification is a central activity in all of the sciences. The category names "bundle" information, providing a means of improved communication and organization; for example, the term conifer efficiently denotes the group of all trees with needles and cones.
In the book Classroom Instruction that Works, the authors cite research that the ability to identify similarities and differences, which is at the heart of classification, is basic to human thought (Marzano, Pickering, and Pollock, 2001).
How Can You Make It Happen?
Classification lessons can begin with a large set of items to be classified. Students discuss the similarities and differences of the items, decide how they will be organized, and place them into groups. They discuss the distinguishing features of each category, and review the items to be sure each is in the correct category. Discussions can include the questions: Are there items that don't fit? Is there a more useful way to classify these items? How can the categories be improved?
To provide more structure in younger grades, students can be given the items and categories. Once the students have mastered classification, give them the items and have them determine the categories to complete the classifying activity. Review the categories that were chosen and discuss how meaningful and useful they are.
When students have an understanding of classifying items into groups, ask them to identify the features that distinguish one category from another and ask them how they decide if something fits into a particular category. Students should be able to defend their classification systems and to identify items that don't fit and explain their reasoning.
Classification can also be used to identify an unknown object by looking at its characteristics and then using a dichotomous key, which is a tool consisting of a series of questions about the features of an item to help identify the item. This is most often used in science to identify items in nature such as shells, rocks, or fish. Players of "20 Questions" are familiar with the use of such keys.