docker - compose错误

Question

这是我的docker-compose.yaml

version: '2'
services:
  databases:
   image: mysql
   ports:
   - "3306:3306"
   environment:
   - MYSQL_ROOT_PASSWORD=password
   - MYSQL_USER=user
   - MYSQL_PASSWORD=password
   - MYSQL_DATABASE=demodb
web:
   image: nginx

错误：The Compose file ./docker-compose.yml' is invalid because: Additional properties are not allowed('web' was unexpected)

在底部，它说这可能是因为docker-compose版本，但在docker网站上，它说windows上的docker带有docker-compose，不需要单独安装。