Environment Variable

While environmental variable is used occasionally, environment variable is overwhelmingly more common:

• Wikipedia: Environment Variable

• Arch Linux wiki: Environment variables

  • "environment var" => 28 instances
  • "environmental var" => 3 instances

• POSIX.1‐2017, Chapter 8. Environment Variables (title)

• Linux man pages:

  • environ(7) -- "Environment variables may be..."
  • getenv(3) -- "get an environment variable"
  • execve(2) -- just "environment"
  • bash(1) -- mostly just "environment", but occasionally "environment variable" and never "environmental"

• Linux kernel

  • git grep -i 'environment var' | wc -l => 183
  • git grep -i 'environmental var' | wc -l => 2

• MSDN

  • getenv() -- "Environment variable name"
  • GetEnvironmentVariable()
  • Environment.GetEnvironmentVariable()

• Python

  • os module

• Perl

  • Env -- "Perl maintains environment variables..."

• Google

  • 

• Stack Overflow

  • An environment-variables tag exists, but environmental-variables does not
  • There are 90,719 results for "environment variable" but only 4,345 results for "environmental variable"

"Environment Variables" is the correct.

And as you have mentioned about MSDN, I would like to further add that on Windows Machine, the start search also shows "Edit the system environment variables" as follows: