Define then discuss

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Define then discuss is a (controversial, but generally followed in practice) pedagogical principle where, when a new idea is introduced, the relevant term (called the definiendum) is first defined as precisely as possible or necessary, and then its significance is discussed. The "discussion" could be carried out interactively, using the formally presented definition as the starting point for exploration.

The discuss could include discussion of:

  • Examples
  • Significance or importance
  • Properties, attributes, or behavior prediction

Exposition contexts

There are three kinds of expositions: in-class explainer exposition, text exposition, and video exposition. In addition, some information could be communicated through means other than exposition.

"Define then discuss" within a single exposition

A typical application of "define then discuss" is within a single exposition (in-class, text, or video). In such a case, the definition has just been presented when the followup discussion occurs. In this scenario, the definition is expected to be fresh in learner's minds as it gets reinforced during discussion.

"Define then discuss" across expositions

Here, the exposition where a definition is provided and the exposition where the discussion happens are different. They could be of the same format (e.g., two successive classes of in-class explainer exposition).

"Define then discuss" split between exposition and exercise

Here, the definition is provided in exposition (in-class, text, or video) and the discussion is carried out through exercises, whether in-class desk work or homework. This works best for mathematical topics where it is possible to reason a priori based on the definition and do various exercises.


  • Examples first is an alternative that begins with a discussion of examples, then abstracts from the examples to construct the definition.


"Define then discuss" works best in scenarios where knowledge of the definition, along with the background knowledge that the learner already possesses, provides the learner with some tool to think about the definiendum, even if this is purely at the formal or superficial level. The tool that the definition provides can be used as a hook for the next step of discussion. The ideal situation is where the entire discussion could be carried out in principle by the learner by himself or herself, even though most learners in practice may not be able to persevere that hard.

Some advantages of the approach are:

  • Having a definition to fall back to gives learners a bare minimum they can always rely upon. For an approach that does not begin with a definition, learners may be more easily disoriented, and there's a greater chance that they may take away nothing from the learning session.
  • Constructing examples or deducing behavior and attributes based on a purely formal definition draws on the learner's background knowledge and also helps practice the retrieval of that knowledge, this allowing for active recall and overlearning of past knowledge.
  • The approach is often more efficient time-wise than alternative approaches such as examples first, even though the latter may engender a deeper understanding of some aspects of the definition. In some cases, time constraints favor this approach.


  • In cases where the definition provides the learner with no tools for thinking about the definiendum, this strategy may not work well. Whether alternate strategies can work better depends on the situation.
  • The approach of having a definition presented to one and then figuring out the attributes does not mimic the process of historical discovery of and refinement of definitions. If we think of learning as a way of repeating in the learner's mind the process of historical discovery, "define then discuss" seems like a bad way of learning.

Criteria for deciding whether to use "define then discuss" or alternate methods

  • Consider time constraints: "Define then discuss" works well in case of limited time, or in case of uncertainty over the amount of time available. Note that examples can be added and explored later if more time becomes available.
  • Consider the extent to which the definition provides a hook for further exploration: In cases where the definition provides some way of facilitating further exploration, this approach works well. In cases where the definition is very difficult to meaningfully work with for exploration, this approach works badly.
  • Consider the extent to which the discussion phase of "define then discuss" will reinforce long-term retention of the definition: The more the act of working through examples or deducing attributes requires one to master the definition, the better.
  • Consider the extent to which the discussion phase of "define then discuss" will reinforce past learning: The more that the act of constructing examples or deducing attributes helps reinforce past knowledge or skills that need to be acquired and honed anyway, the better this approach works.

Note that any comparative analysis would also consider whether the alternate methods work well in the context. Some definitions may be fertile for exploration, but the examples first approach may also be very promising. In contrast, some definitions may be extremely opaque regardless of the approach we use.