- Correct "线程组" (thread group) to "进程组" (process group) in tutorials/mpi-reduce-and-allreduce/zh_cn.md
- Correct "减少" (reduce as verb) to "归约" (reduction as noun) in tutorials/introduction-to-groups-and-communicators/zh_cn.md

These changes align the Chinese translation with standard MPI terminology, ensuring accuracy for Chinese-speaking learners.