This is the 423rd most frequent Chinese word.
专业
"专业" means "major" or "specialty" in academics or a "profession/expertise" in a field.
Here, "专业" is used to describe someone as being professional or having expertise in a certain domain.
他在设计方面非常专业。
He is very professional in the field of design.
In this sentence, "专业" refers to an academic major or field of specialization in school.
我的专业是计算机科学。
My major is Computer Science.
In this case, "专业" qualifies "服务" (services) as professional, emphasizing quality and expertise.