specialize
v.v. to focus most of your time and effort on one specific subject, skill, or area of work.
v. to concentrate one's efforts or interests on a particular field of study, professional activity, or biological niche. Intransitive — requires a prepositional phrase to specify the area of focus.
I want to specialize in international law after I graduate.
Many local bakeries choose to specialize in gluten-free products to meet the growing demand from health-conscious customers.
While general practitioners provide a broad range of care, many medical students eventually choose to specialize in fields like cardiology or neurology to master more complex procedures.
From special + -ize.
The verb is intransitive and almost always takes the preposition 'in' before the subject of focus.
He specializes international lawHe specializes in international lawSpecialize is an intransitive verb and requires the preposition 'in' to connect to its object.