il·lus·tra·tion

/ˌıləˈstreıʃən/ noun, pl -tions

1 [count] : a picture or drawing in a book, magazine, etc.

The illustration on page 30 shows the parts of an engine.

a book with many photographs and illustrations

2 [count] : an example or story that is used to make something easier to understand

The illustrations that he provided in his speech were very effective.

3 [noncount] : the act or process of illustrating something: such as

3 a : the act or process of producing or providing pictures for a book, magazine, etc.

They selected photographs to use for the illustration of the book.

3 b : the act or process of giving examples to make something easier to understand

Illustration is the key to good communication.

By way of illustration, [=as an example] let us examine this poem.