1.
population
The number of people living in a particular area, country, or the world.
人口 is composed of 人 (person) + 口 (mouth/opening, here meaning 'count').
COMMON COLLOCATIONS:
- 人口が増える: population increases
- 人口が減る: population decreases
- 人口密度: population density
- 人口問題: population problem
- 高齢化人口: aging population
RELATED TERMS:
- 少子化: declining birthrate
- 過疎: depopulation (of rural areas)
- 過密: overcrowding