You pick up a suitcase and groan — it is おもい (heavy). Then you grab your laptop bag and sigh with relief — it is かるい (light). These two い-adjectives describe physical weight, but in Japanese they go much further. Both おもい and かるい have rich figurative meanings that describe personalities, situations, and emotional states. Once you know all their uses, you will start spotting them everywhere in everyday Japanese conversation.
YukaQuick question, Rei — when should I use omoi versus karui?
ReiAh, a classic mix-up! They’re related but definitely not interchangeable. I’ll explain with examples and it’ll make perfect sense.
At a Glance: おもい vs かるい
| Feature | おもい (omoi) 重い | かるい (karui) 軽い |
|---|---|---|
| Meaning | Heavy / serious / grave | Light / minor / casual / easy-going |
| Word type | い-adjective | い-adjective |
| Kanji | 重い | 軽い |
| Negative | 重くない (omokunai) | 軽くない (karukunai) |
| Past tense | 重かった (omokatta) | 軽かった (karukatta) |
| Te-form | 重くて (omokute) | 軽くて (karukute) |
| Adverb | 重く (omoku) | 軽く (karuku) |
| JLPT level | N5 | N5 |
おもい (重い) — Heavy and Serious
おもい is an い-adjective describing something heavy in weight. The kanji 重 (also read じゅう or ちょう) means “weight” or “layering,” and appears in many Japanese compounds. Beyond physical weight, おもい carries strong figurative meanings that are essential for natural Japanese.
Figurative meanings of おもい:
| Context | Japanese example | Meaning |
|---|---|---|
| Physical weight | このスーツケースは重い | This suitcase is heavy. |
| Serious/grave (situation) | 重い責任 | A grave/heavy responsibility |
| Serious (illness) | 病気が重い | The illness is serious/severe. |
| Emotionally intense (person) | あの人は重い | That person is emotionally intense/clingy. |
| Slow/sluggish | パソコンが重い | The computer is slow (heavy to operate). |
Example sentence 1:
この荷物はとても重い。
Kono nimotsu wa totemo omoi.
This luggage is very heavy.
Example sentence 2:
責任が重くてプレッシャーを感じる。
Sekinin ga omokute puresshā o kanjiru.
The responsibility is heavy and I feel pressured.
Example sentence 3 (colloquial):
あいつは重いから、なかなか別れられない。
Aitsu wa omoi kara, nakanaka wakaraenai.
That person is emotionally intense (clingy), so it’s hard to break up.
YukaOh interesting! So omoi can mean that too? I only knew the basic meaning.
ReiYes! omoi is more versatile than most learners realize. Native speakers use it in all sorts of situations — not just the obvious ones.
かるい (軽い) — Light and Casual
かるい is an い-adjective describing something light in weight. The kanji 軽 contains the “vehicle/cart” radical (車) on the left, suggesting something that moves easily — light enough to roll. Like おもい, かるい extends far beyond physical weight in everyday Japanese usage.
Figurative meanings of かるい:
| Context | Japanese example | Meaning |
|---|---|---|
| Physical weight | このバッグは軽い | This bag is light. |
| Minor (symptom) | 軽い風邪 | A mild/minor cold. |
| Easy / casual | 軽い運動 | Light exercise / easy workout |
| Flippant / not serious (person) | 口が軽い | A person who can’t keep secrets (loose-lipped) |
| Carefree attitude | 軽い気持ちで | In a casual/lighthearted mood |
Example sentence 1:
このリュックはとても軽い。
Kono ryukku wa totemo karui.
This backpack is very light.
Example sentence 2:
軽い運動を毎日しています。
Karui undō o mainichi shite imasu.
I do light exercise every day.
Example sentence 3 (figurative):
彼は口が軽いから、秘密を話さないで。
Kare wa kuchi ga karui kara, himitsu o hanasanai de.
He’s loose-lipped, so don’t tell him any secrets.
YukaWhat about karui? Is it used as often as omoi in daily conversation?
Reikarui is super common too! The two words actually complement each other really well once you understand both.
Side-by-Side Comparison Table
| Category | おもい (omoi) 重い | かるい (karui) 軽い |
|---|---|---|
| Physical weight | Heavy (weighs a lot) | Light (weighs little) |
| Severity (illness/duty) | Serious / grave | Mild / minor |
| Computer/phone speed | Slow / sluggish | Fast / responsive |
| Personality | Emotionally intense / clingy | Carefree / flippant / loose-lipped |
| Mouth (口が〜) | 口が重い = reserved / tight-lipped | 口が軽い = loose-lipped / talkative |
| Te-form use | 重くて = heavy and… / so heavy that… | 軽くて = light and… / so light that… |
Common Mistakes English Speakers Make
Mistake 1: Limiting these words to physical weight
English speakers often use おもい and かるい only for physical objects. But native Japanese speakers use them constantly in figurative contexts: パソコンが重い (the computer is slow), 軽い気持ちで (casually/lightheartedly), 重い話 (a heavy/serious topic). Ignoring the figurative layer means missing half the vocabulary.
Mistake 2: Not knowing 口が重い / 口が軽い
These two fixed expressions are extremely common in Japanese conversation. 口が重い (kuchi ga omoi) = someone who rarely speaks / keeps secrets well. 口が軽い (kuchi ga karui) = someone who talks too much / can’t keep a secret. Knowing these phrases will make you sound much more natural.
Mistake 3: Forgetting the Te-form connects to reasons
重くて and 軽くて can be used to chain adjectives and explain reasons. このバッグは軽くて使いやすい (This bag is light and easy to use). 荷物が重くて持てない (The luggage is so heavy I can’t carry it). Practice connecting おもい and かるい with て to express complex thoughts naturally.
Decision Flowchart: おもい or かるい?
Use this flowchart when choosing between these adjectives:
What are you describing?
├─ Physical weight
│ ├─ Weighs a lot / hard to lift → 重い (omoi)
│ └─ Weighs little / easy to carry → 軽い (karui)
├─ Illness or symptom
│ ├─ Severe / serious → 重い (omoi)
│ └─ Mild / minor → 軽い (karui)
├─ Device / computer speed
│ ├─ Slow → 重い (omoi)
│ └─ Fast / responsive → 軽い (karui)
└─ Person’s attitude or speech
├─ Emotionally intense / clingy → 重い (omoi)
├─ Tight-lipped / reserved → 口が重い
└─ Talkative / loose-lipped → 口が軽い
Quick Quiz
YukaAlright, I think I understand both now. Time for a quiz to check!
ReiThat’s the spirit! Testing yourself is one of the best study techniques. Ready?
Fill in the blank with おもい or かるい (in correct form). Answers below.
1. このスーツケースは___くて、一人では持てない。(This suitcase is so heavy I can’t carry it alone.)
2. 新しいノートパソコンは___くて持ち運びに便利だ。(The new laptop is light and convenient to carry around.)
3. 彼女は少し___と思う。依存しすぎじゃない？(I think she’s a bit emotionally intense. Isn’t she too dependent?)