The term “segregation” is used in the CQRS pattern.
What’s the difference between segregation versus separation in this case?
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To try and answer your question, lets look at where the pattern came from.
Command Query Separation (CQS) where the querying will not change the state of the object (Only the commands would). The key point (in this context) is a class would consist of both Commands and Queries.
Command Query Responsibility Segregation (CQRS), holds the same principal logic (commands can alter the state and queries do not alter the state) and takes it one step further. Where the Commands are in different classes (even a different model) to the Queries.
As mentioned the Separation and Segregation are synonymous in the English language, however the patterns model their classes slightly differently to achieve this goal.
this is my understanding, and hopefully this may shed light on the context.