A real number is any number that has a decimal representation.
```mermaid
flowchart LR
A["Natural \n Numbers"]
B["Zero"]
C["Negatives \n of natural \n numbers"]
D["Integers (Z)"]
E["Noninteger \n ratios of \n integers"]
F["Rational \n numbers (Q)"]
G["Irrational \n numbers (I)"]
H["Real numbers (R)"]
A & B & C --> D
D & E --> F
F & G --> H
```