Translation guide
Sputum is mucus coughed up from the respiratory tract. In Japanese, the most common word is 痰 (たん), but medical contexts may use 喀痰 (かくたん).
The general term for phlegm or sputum, used in everyday and medical contexts.
痰 (たん) is the everyday word for phlegm or sputum. 喀痰 (かくたん) is a technical medical term specifically for expectorated sputum, often used in test names like 喀痰検査 (sputum test).