Translation guide
The state of feeling sluggish, lacking energy, or being mentally/physically slow. In Japanese, this is expressed through nouns, adjectives, and descriptive phrases that convey tiredness, lack of motivation, or drowsiness.
Describing a state of physical or mental sluggishness, often due to tiredness, illness, or mood.
A common medical/formal term for a feeling of lethargy or malaise. Often used in health contexts.
最近、倦怠感が続いています。
Lately, I've been feeling lethargic.
Casual, everyday word for physical sluggishness or heaviness. Commonly used when feeling tired or unwell.
今日はなんだかだるさが抜けない。
I just can't shake this lethargy today.
Literally 'motivation doesn't come out.' Used when you lack the drive to do anything, often overlapping with lethargy.
暑さでやる気が出ない。
The heat makes me feel lethargic.
Apathy or listlessness; a psychological state of having no energy or will. Stronger than just tiredness.
無気力で何も手につかない。
I'm so lethargic I can't focus on anything.
When lethargy is specifically about feeling sleepy or sluggish due to lack of sleep.
Drowsiness or sleepiness. Use when the lethargy is clearly from needing sleep.
昼食後、強い眠気に襲われた。
After lunch, I was hit by a wave of lethargy.
To zone out or feel spaced out, often from tiredness. Implies mental lethargy.
寝不足でずっとぼーっとしている。
I'm feeling lethargic and spaced out from lack of sleep.
Lethargy as a symptom of illness or a chronic condition.
A sense of fatigue, often used in medical contexts. More about tiredness than motivation.
原因不明の疲労感が続く。
I have persistent lethargy of unknown cause.
Chronic fatigue. Used for long-term lethargy, often as a medical term.
慢性疲労で日常生活に支障が出ている。
Chronic lethargy is interfering with my daily life.
The specific lethargy many feel during hot, humid summer weather.
Summer fatigue or heat exhaustion. A very common term for the lethargy caused by summer heat.
今年の夏は特に夏バテがひどい。
This summer, my lethargy is especially bad.
倦怠感 (kentaikan) is a formal, often medical term for malaise. だるさ (darusa) is casual and describes physical heaviness. 疲労感 (hirōkan) is a general sense of fatigue, less clinical than 倦怠感 but still somewhat formal.
風邪で倦怠感がある。
I feel lethargic from a cold. (formal/medical)
今日はだるくて動けない。
I'm so lethargic I can't move today. (casual)
仕事の後はいつも疲労感が強い。
I always feel strong lethargy after work. (general fatigue)
There is no single Japanese word that perfectly matches 'lethargy' in all contexts. Using a direct translation like 嗜眠 (shimin, 'lethargy' as a medical term) is rare and overly technical. Choose the expression based on the cause and context.
嗜眠状態
lethargic state (medical jargon, not for everyday use)