an ordinary person; someone without exceptional abilities or talents.
彼の考え方は常人には理解しがたいところがある。
There are aspects of his thinking that ordinary people find hard to understand.
常人であればその仕事を一人で片付けるのは難しいだろう。
For an ordinary person, it would probably be difficult to finish that job alone.
作家は常人とは違う鋭い観察力を持っていることが多い。
Writers often have a keen observational ability that differs from ordinary people.