snake_case

Example: user_name, max_value

Why?

• Highly readable thanks to underscores.
• Inherited from early languages (C, Python).
• Commonly used in databases (PostgreSQL, MySQL) where case-insensitivity matters.

Practical example

user_name = "Alice"
max_value = 100

Advantages: clear, universal. Disadvantage: verbose to type (Shift + _).