To divide is to break something down, identifying or analyzing its components. It’s far easier to take in a subject, especially a complex one, a piece at a time. The thing divided may be as concrete as a medical center (which you might divide into specialty units) or as abstract as a knowledge of art (which you might divide into sculpture, painting, drawing, and other forms). To classify is to make sense of a potentially bewildering array of things — works of literature, this year’s movies — by sorting them into categories (types or classes) that you can deal with one at a time. Literature is customarily arranged by genre — novels, stories, poems, plays. Movies might be sorted by audience (children, teenagers, mature adults). Dividing and classifying are like two sides of the same coin. In theory, any broad subject can be divided into components, which can then be classified into categories. In practice, it’s often difficult to tell where division stops and classification begins.

In his college textbook Wildlife Management (San Francisco: Freeman, 1978), Robert H. Giles Jr. uses division to simplify an especially large, abstract subject: the management of forest wildlife in America. To explain which environmentalists assume which duties, Giles divides forest wildlife management into six levels or areas of concern, arranged roughly from large to small, all neatly presented in fewer than two hundred words.

There are six scales of forest wildlife management: (1) national, (2) regional, (3) state or industrial, (4) county or parish, (5) intra-state region, management unit, or watershed, and (6) forest. Each is different. At the national and regional levels, management includes decisions on timber harvest quotas, grazing policy in forested lands, official stance on forest taxation bills, cutting policy relative to threatened and endangered species, management coordination of migratory species, and research fund allocation. At the state or industrial level, decision types include land acquisition, sale, or trade; season setting; and permit systems and fees. At the county level, plans are made, seasons set, and special fees levied. At the intra-state level, decisions include what seasons to recommend, what stances to take on bills not affecting local conditions, the sequence in which to attempt land acquisition, and the placement of facilities. At the forest level, decisions may include some of those of the larger management unit but typically are those of maintenance schedules, planting stock, cutting rotations, personnel employment and supervision, road closures, equipment use, practices to be attempted or used, and boundaries to be marked.

In a textbook lesson on how babies develop from Human Development (New York: Freeman, 1984), Kurt W. Fischer and Arlyne Lazerson describe a research project that classified babies into three types by temperament.

The researchers also found that certain of these temperamental qualities tended to occur together. These clusters of characteristics generally fell into three types — the easy baby, the difficult baby, and the baby who was slow to warm up. The easy infant has regular patterns of eating and sleeping, readily approaches new objects and people, adapts easily to changes in the environment, generally reacts with low or moderate intensity, and typically is in a cheerful mood. The difficult infant usually shows irregular patterns of eating and sleeping, withdraws from new objects or people, adapts slowly to changes, reacts with great intensity, and is frequently cranky. The slow-to-warm-up infant typically has a low activity level, tends to withdraw when presented with an unfamiliar object, reacts with a low level of intensity, and adapts slowly to changes in the environment. Fortunately for parents, most healthy infants — 40 percent or more — have an easy temperament. Only about 10 percent have a difficult temperament, and about 15 percent are slow to warm up. The remaining 35 percent do not easily fit one of the three types but show some other pattern.

When you divide and classify, your point is to make order out of a complex or overwhelming jumble.