Primary and replica are the preferred terms.

The current situation is master/replica, with slave kept as an alias of replica. Some commands like ROLE still returns "master" and "slave".

So far "master" was accepted, so there aren't yet any aliases for "master". Let's introduce aliases and deprecate master.

1. Add aliases for master (not a breaking change)
2. Delete master and slave terminology (breaking change) EDIT: After feedback, we've decided to skip the breaking changes. We can only that as a client opt-in. See [NEW] Opt-in for inclusive language (primary/replia in ROLE reply, CLUSTER SHARDS, etc.) #751.

Occurrences of "master" where we can add "primary" and make "master" an alias:

• CLIENT KILL TYPE MASTER
• CLIENT LIST TYPE MASTER
• SENTINEL GET-MASTER-ADDR-BY-NAME

Note: This issue was edited to not include any breaking changes. The initial suggestion included breaking changes, but this was not appreciated by the users. Thus, the downvotes.