I am offering ten principles for writing material for educational courses. The second principle is about defining your terms.

1. Principle 2
Define terms
Glenn Martin
March 2017

2.  Define your terms, then use those terms
consistently throughout the course.

3.  Question:
 Does the material involve terms that:
• are likely to be unfamiliar to students? or
• will be used with a different meaning to the meaning
students are familiar with?
Example: in a Physics course, “force” has a particular
meaning – mass times acceleration.
[In general conversation, people use words in ways that
are consistent with the definitions found in common
dictionaries.]

4. If a term needs to be defined, keep this in mind:
 A good definition differentiates between what is
“the thing” and what is not “the thing”.

5.  A good definition makes it as clear as possible
what is the thing that is being defined, and what
is not “the thing”.
 The importance of a good definition is that it
enables us to differentiate “the thing” from other
things with which it could be confused.
 Example: How would you define “power”?

6. Suppose we have a
definition of “power”.
If it is a good definition,
it will clarify the distinctions
between power and other
concepts with which it
might be confused.

7. Is one concept
a subset of the
other? (A or B)
A B
C
Do the concepts overlap? (C)
D
What are the connections
between the concepts? (D)

8. If a term is used in a way that is different from what
would be found in a common dictionary, there must
be justification for the specialised use. This
includes:
 authority for the new meaning (e.g. academic
source)
 need for the new meaning (e.g. in order to
explain phenomena)
 proposed application of the new meaning.

9.  Having defined a term in a particular way, it must
be used with that meaning consistently
throughout the course.
 Care is needed not to, at any point, confuse the
ordinary sense in which a term is used with the
meaning it has been assigned in the course.