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専門， せんもん
1. speciality, specialty, special subject of study, area of expertise, (one's) field, (one's) major
2. sole interest, single focus, concentrating exclusively on, doing exclusively, sticking to
专门
は
1. indicates sentence topic
2. indicates contrast with another option (stated or unstated)
3. adds emphasis
指示句子的主题；表示与另一选项（无论是否明确提及）形成对比；表示强调
