Q.What different criteria would you choose to classify people that you meet often?

Classification means placing things into convenient categories on the basis of easily observable characters, and the same idea can be applied to people we meet often. We simply choose features that are easy to notice and that group people usefully.

Some criteria one might choose are:

• Where they live or come from — locality or region.
• Their age group — children, adults, the elderly.
• Their work or occupation — teacher, doctor, shopkeeper, student.
• The language they speak.
• The relationship they have with us — family, friends, neighbours, classmates.

Exactly which criteria are "best" depends on the purpose behind the grouping, just as scientific classification chooses characters that make the study of organisms easier.

At its heart, classification is nothing more than placing things into convenient categories on the basis of characters that are easy to observe. We do this instinctively in everyday life: the moment we say "a teacher", "a neighbour" or "a classmate", a set of associated features comes to mind. The same instinct can be turned deliberately on the people we meet from day to day.

The criteria we might choose include:

• Locality or origin — grouping people by the place they live in or come from, much as local names for organisms shift from region to region.
• Age — sorting people into children, young people, adults and the elderly.
• Occupation — grouping by what people do, such as teachers, doctors, shopkeepers, farmers or students.
• Language — the tongue a person speaks.
• Relationship to us — family, friends, neighbours, colleagues or classmates.

What matters is that the chosen character is easy to observe and that it separates people into groups that are useful for our purpose. A person can also belong to several categories at once — a single individual may be an adult, a teacher and a neighbour — which mirrors how organisms sit within categories at different levels.