Translation guide
A mouth ulcer is a painful sore inside the mouth. In Japanese, the most common and natural term is 口内炎 (こうないえん), which covers canker sores and general mouth ulcers. Other terms exist for specific types or locations.
The most common way to refer to a painful sore inside the mouth, including canker sores.
This is the standard medical and everyday term for a mouth ulcer or canker sore. It is widely understood and used in both casual and formal contexts.
口内炎ができて痛い。
I have a mouth ulcer and it hurts.
口内炎に効く薬を探しています。
I'm looking for medicine that works on mouth ulcers.
Specifically refers to aphthous stomatitis, the most common type of recurring mouth ulcer. More precise than 口内炎, often used in medical contexts.
アフタ性口内炎は再発しやすい。
Aphthous ulcers tend to recur.
When the sore is specifically on the tongue.
Refers to inflammation or ulceration of the tongue. It can be used for tongue ulcers, but is less specific than 口内炎 for a single sore.
舌炎ができて食事がつらい。
I have a tongue ulcer and eating is painful.
When the sore is on the lip or gum area.
In Japanese, you typically say 口内炎ができる (to get a mouth ulcer) rather than 口内炎がある (to have a mouth ulcer). The verb できる implies something has appeared or formed, which is more natural for sores.
口腔潰瘍 (こうくうかいよう) is the direct medical translation of 'oral ulcer,' but it is very technical and rarely used outside of medical documents. Stick with 口内炎 for everyday use.