1.
dry cough
A cough that produces no phlegm. A non-productive cough.
空咳が止まらない。
I can't stop my dry cough.
風邪の後、空咳だけが残った。
After my cold, only a dry cough remained.
乾燥した空気のせいで空咳が出る。
The dry air is causing a dry cough.
2.
fake cough; deliberate cough
A cough made on purpose to get someone's attention, signal discomfort, or cover an awkward silence.
彼は空咳をして注意を引いた。
He gave a fake cough to get attention.
気まずい沈黙の中、誰かが空咳をした。
In the awkward silence, someone gave a deliberate cough.
先生が空咳をすると、生徒たちは静かになった。
When the teacher cleared his throat, the students fell silent.
空咳 has two distinct meanings: a dry cough (medical) and a deliberate cough (social).
WORD FORMATION:
The prefix 空 means "empty" or "lacking content," as in 空っぽ (empty) and 空振り (a swing and a miss). Here it indicates a cough with no phlegm, or a cough with no real need to cough.
MEDICAL SENSE:
A dry, non-productive cough. Contrasts with 痰の絡む咳 (a productive cough with phlegm). Common with colds, allergies, and dry air.
SOCIAL SENSE:
A deliberate cough used to get attention, signal discomfort, or break an awkward silence. The standard expression is 空咳をする.
COMMON PATTERNS:
- 空咳が出る: to have a dry cough
- 空咳が止まらない: can't stop coughing (dry)
- 空咳をする: to give a deliberate cough