Multiuser : Unix supports multiple users simultaneously, allowing them to interact with the system and run their own processes independently.

Multitasking : Unix can execute multiple processes concurrently, switching between them rapidly to give the illusion of simultaneous execution.

Hierarchical file system : Unix organizes files and directories in a hierarchical tree structure, with the root directory at the top and subdirectories branching out from there.

Shell : Unix provides a command-line interface called the shell, which allows users to interact with the system by typing commands. The shell interprets these commands and executes them, providing a powerful way to manipulate files, run programs, and manage system resources.

Portability : Unix was designed to be highly portable, meaning it can run on a wide range of hardware platforms with minimal modifications. This has contributed to its widespread adoption and longevity.

Unix has many variants, including the original AT&T Unix, BSD Unix (Berkeley Software Distribution), and various commercial versions like Solaris, AIX, and HP-UX. It also served as the inspiration for open-source Unix-like operating systems such as Linux.