This is the 7420th most frequent Japanese word.
作用
"作用" means "action, effect, or function."
In this sentence, '作用' is used to describe the effect or action exerted by the medicine on the body.
薬の作用で熱が下がった。
The fever decreased due to the effect of the medicine.
Here, '作用' refers to the influence or impact that the chemical substance has on plants.
その化学物質は植物に有害な作用を及ぼす可能性がある。
That chemical substance might exert a harmful effect on plants.
In this instance, '作用' denotes the beneficial influence yoga has on mental well-being.