増加
ぞうか · zouka · JLPT N3 · noun
addition
📈 増加 = increase (増) + add (加): growing by adding more
増 (ぞう) is the 'increase' in 増える, to grow in number. 加 (か) is the 'add' in 加える and in 参加, to join. Put them together and you get growth by adding: 人口の増加 is a rise in population.
加 — force 力 + mouth 口
加 is traditionally analyzed as a compound of 力 (strength) and 口 (mouth), suggesting boasting or exaggerating one's effort with words. From this it extended to the meaning 'to add' or 'increase'. Today it is used broadly for addition, both literal and figurative.