master/slave

In computing, engineering, and electronics, master/slave is a technical metaphor describing a relationship where one device or process (the master) has unidirectional control over another (the slave). Historically, this terminology has been applied to hard drive configurations (PATA/IDE), database replication, and communication protocols. In these setups, the "master" unit typically asserts control, manages resources, or serves as the authoritative source of data, while the "slave" unit obeys commands or replicates the data of the master.

The use of this terminology is highly contested. Those who continue to use it often cite technical tradition, arguing that the terms are standard industry jargon that effectively describe a dependency hierarchy without intending to reference human rights violations. However, a significant portion of the technology sector argues that using metaphors derived from the institution of human slavery is unnecessary, exclusionary, and racially offensive. Critics also point out that the metaphor is often technically inaccurate for modern systems where communication is bidirectional or cooperative. As a result, major organizations including the IEEE, Python, GitHub, and the Linux kernel have formally adopted more descriptive alternatives.

Example:
"To improve read performance, the application writes data to the master database and reads from the slave instances."

Example:
"Ensure the jumper settings on the hard drive are correctly set to master or slave depending on its position on the ribbon cable."