👉 In mathematics, an illusion is a phenomenon where two different mathematical objects appear to be identical. This can happen because of various factors such as the use of different conventions or models, the presence of hidden information, or even due to a misunderstanding of the mathematical structure itself.
For example, consider the following diagram:
```
A
|
/ \
B | C
|
D
E
|
F
|
G
|
H
illusory