This is the 7834th most frequent Japanese word.
咳
Cough.
In this sentence '咳' refers to the act of coughing and is used as a noun to describe a persistent action.
彼はひどい咳が止まらない。
He cannot stop coughing badly.
Here, '咳をする' means 'to cough', demonstrating its usage as part of a verbal expression formed with the verb 'する'.
咳をする時は口を覆いましょう。
When coughing, cover your mouth.
In this sentence, '咳' indicates a symptom being targeted by medication, serving as the object of relief.