# data[].attributes.body
-16th Century , Robert Recorde create an "=" symbols because he tired to write "equal to"

# data[].attributes.body
-to avoid repeating and avoid using many words
-to write by short term

# data[].attributes.headline
The function of letters as math symbols 

# data[].attributes.subject
The function of letters as math symbols 

# data[].attributes.body
-to represent sets of number and equation

# data[].attributes.headline
The function of using others symbol as math symbol 

# data[].attributes.subject
The function of using others symbol as math symbol 

# data[].attributes.body
- ! , factorial , is the product of all positive integers less than or equal to n
-π , specific number ( 3.142)
-x , multiplication
-e, repeated multiplication
-Σ , represent all range number