tion.

Definition. One of the simplest ways of explaining is to define a
term. Dictionary definitions are familiar to everyone. In a great
many instances the dictionary definition is by means of synonyms.
While this is a convenient, easy method it is seldom exact. Why?
Recall what you learned concerning the meanings of synonyms. Do they
ever exactly reproduce one another's meanings? There is always a
slight degree of inaccuracy in definition by synonym, sometimes a
large margin of inexactness. Is the following a good definition?

A visitor to a school began his address: "This morning,
children, I propose to offer you an epitome of the life of
St. Paul. It may be perhaps that there are among you some too
young to grasp the meaning of the word _epitome_. _Epitome_,
children, is in its signification synonymous with synopsis!"

London Tid-Bits

Logical Definition. An exact definition is supplied by the logical
definition. In this there are three parts--the term to be defined,
the class (or genus) to which it belongs, and the distinguishing
characteristics (differentia) which mark it off from all the other
members of that same class. You can represent this graphically by
inclosing the word _term_ in a small circle. Around this draw a larger
circle in which you write the word _class_. Now what divides the term
from the class in which it belongs? Indicate the line around the
_term_ as _distinguishing characteristics_, and you will clearly see
how accurate a logical definition is. The class should be just larger
than the term itself. The main difficulty is in finding exact and
satisfying distinguishing characteristics. There are some terms which
are so large that no classes can be found for them. Others cannot be
marked by acceptable distinguishing characteristics, so it is not
possible to make logical definitions for all terms. Consider such
words as _infinity, electricity, gravity, man_.

The words of the definition should be simple, more readily understood
than the term to be defined.

Term Class Distinguishing characteristics

A biplane is an airplane with two sets of supporting
surfaces.

A waitress is a woman who serves meals.

Narration is that form of discourse which relates events.

A word is a combination of suggesting an idea.
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A dictiona