Before an operating system can read from or write to a hard disk, the file system must be mounted on one of the hard disk's partitions!
In English, the term "mounting" is used, which can mean attachment, support, assembly, installation, suspension, socket, ...!
A "mounted" disk is available to the operating system as a file system for reading, writing, or both. However, it can refer to a group of files in a file system that can be accessed by a user or a group of users. Often it is also associated with virtual media!