To increase or become more numerous; to multiply (intransitive). Note: 殖える is often used for population growth or capital appreciation.
スマホのユーザーが年々増えている。
The number of smartphone users is increasing year by year.
貯金が少しずつ増えたので安心だ。
My savings have gradually increased, so I'm relieved.
新しいサービスが始まって登録者数が増えた。
After launching the new service, the number of registrants increased.
細菌が培養で増える様子を観察した。
I observed bacteria multiplying in culture.