Node.js - 'nodemon' is not recognized as an internal or external command

I found the solution:

I installed nodemon locally and this command works only if the nodemon was installed globally.

For the locally installed nodemon I inserted it into "scripts" inside the package.json file like this:

  "scripts": {
    "start": "nodemon index.js"
  },

and I run the index.js file using:

npm start

Second solution is to install nodemon globally with npm:

npm install -g nodemon

or Yarn:

yarn global add nodemon