～だけ／～しか～ない

How it works

Both patterns translate as only, but they are built differently. だけ attaches to a noun, a number or a plain-form clause and the verb stays as it is: 野菜だけ食べます. しか also attaches to the noun, but the verb must be negative: 野菜しか食べません. That negative is grammatical, not semantic: 野菜しか食べません still means 'I eat only vegetables', not 'I don't eat vegetables'.

だけ simply draws a line around a quantity or a set; it is neutral and can even sound positive (少しだけください = just a little, please). しか…ない adds the speaker's judgment that what is inside the line is little, insufficient or disappointing: 百円しかない = I have only a hundred yen, and that is not enough.

Particles: だけ may be followed by を／が (野菜だけを食べる) or drop them. しか replaces を and が entirely, but keeps に, で, と, へ and から in front of it: 東京でしか買えません, 田中さんとしか話しません, 週末にしか会えません. Because it so often describes what is not possible, しか pairs naturally with the potential negative (使えません, 休めません).

Examples

• 今日は野菜だけ食べました。 きょう は やさい だけ たべました。 Today I ate only vegetables.
• 財布には百円しかありません。 さいふ に は ひゃくえん しか ありません。 I only have a hundred yen in my wallet.
• 日本語は少しだけ分かります。 にほんご は すこし だけ わかります。 I understand just a little Japanese.
• 会議には田中さんだけ来ました。 かいぎ に は たなかさん だけ きました。 Only Mr Tanaka came to the meeting.
• この店は現金しか使えません。 この みせ は げんきん しか つかえません。 This shop only takes cash.
• 昨日は三時間しか寝ていません。 きのう は さんじかん しか ねていません。 I only slept three hours last night.

Compare with

• だけ vs しか with the same fact: 三人だけ来ました states that three came; 三人しか来ませんでした adds that the speaker expected more.
• ～ばかり (N4) means 'nothing but' as a habit, usually critical: ゲームばかりしている (all he does is play games). It limits an activity, not a quantity. The look-alike ～たばかり ('just did') is a completely different pattern.
• ～のみ is the formal, written cousin of だけ, common on signs and notices: 関係者のみ (staff only).

Traps for Spanish, English and French speakers

• English I only have 100 yen and Spanish solo tengo cien yenes are affirmative, so learners keep an affirmative verb after しか: ×百円しかあります. しか demands the negative: ○百円しかありません. French speakers have an ally in ne…que (je n'ai que cent yens), which works exactly like しか…ない.
• Reading しか…ない as a true negative: English speakers translate 三人しか来ませんでした as 'three people didn't come'. It means 'only three people came'; the negative is demanded by しか and carries no negative meaning of its own.
• Keeping the object particle, because Spanish solo, English only and French seulement are plain adverbs: ×水をしか飲みません, ×日本語をだけ話します. しか always replaces を／が (○水しか飲みません); だけ takes を／が after it or nothing at all (○日本語だけ話します, 日本語だけを話します).
• Using だけ for every solo / only / seulement turns complaints into choices: 三時間だけ寝ました sounds like 'I chose to sleep just three hours'. For 'I only managed three hours' use しか: ○三時間しか寝ていません.