He is a specialist fool, with no interest in anything outside his field.

He couldn't say anything about issues outside of his field of expertise.

There are many different specialty stores in this town.

An old person was playing with his grandchild in the park.

An old person was walking in the park.

He is known as an expert in gerontology.

My grandfather is interested in gerontology.

My grandmother lives in a nursing home.

My grandmother participates in the local old people's club every week.

My house is near the mountains.