This is probably due to a broken installation. I would suggest you install behat with composer, if you want it globally installed then run
$ composer global require behat/behat
Then make sure you add the composer path to your $PATH
variable.
Its much easier to work with behat as a local dependency of your project. I am not sure if you are using it for a PHP project but if you are then i'd recommend not to install it globally, instead in your composer.json file add it as a dev dependency:
{
"require-dev": {
"behat/behat": "~3.0"
}
}
Then run composer update
to get it installed locally. You can then access it by running vendor/bin/behat
.
From personal experience, installing behat globally can give you issues because of other local libraries you may need per project basis. This may have been resolved now but I had issues when one local project behat dependency differed from another projects.