The number of people living in a particular area or country; population (including aspects like growth or density).
都市部の人口は年々増加している。
The population of urban areas is increasing year by year.
この国の総人口は約一億人だ。
The total population of this country is about 100 million.
人口密度が高い地域では住宅問題が深刻だ。
In areas with high population density, housing problems are serious.
Public talk or common discourse—what people generally say; historically used to mean something that becomes the talk of the people.
その噂はすぐに人口に上って町中の話題になった。
The rumor quickly became common talk and was the town's topic.
古いことわざで『人口に膾炙する』という表現がある。
There is an old expression meaning 'to become widely known'—'jin kō ni kaisha suru' (to be talked about by the public).