ไม่ได้: didn't and can't

You'll hear ไม่ได้ all the time, and it has two meanings. Its position decides which one: before the verb it means “didn't”, after the verb it means “can't”.

Plain ไม่ is usually not enough for a single action in the past. As the Negation topic shows, ไม่กิน means “I don't eat” or “I won't eat”, and isn't the normal way to say “I didn't eat”. For last night's dinner you'd say ผมไม่ได้กิน. States and qualities keep plain ไม่ even in the past: เมื่อวานผมไม่สบาย means “I wasn't well yesterday”.

The same ไม่ได้ can also deny one particular claim. ผมไม่ได้บอกอย่างนั้น means “I didn't say that”, often implying you said something else. It doesn't have to be about the past: ผมไม่ได้ล้อเล่น means “I'm not joking”.

After the verb, ไม่ได้ means something else: it can't be done, or it isn't allowed. This is the ได้ of “can” from “Can, must, want”, now negated. กินได้ means “I can eat it”, and กินไม่ได้ means “I can't eat it”.

• เมื่อวานmʉ̂a-waanyesterdayผมpǒmIไม่ได้mâi-dâididn'tไปbpaigoทำงานtam-ngaanwork

  I didn't go to work yesterday.

• ผมpǒmIไม่ได้mâi-dâididn'tกินgineatข้าวkâaorice, a meal

  I didn't eat.

• ผมpǒmIกินgineatข้าวkâaorice, a mealไม่ได้mâi-dâican't

  I can't eat.

  The same four words as above. ไม่ได้ has moved to the end, so “didn't eat” has become “can't eat”.

• ผมpǒmIไม่ได้mâi-dâididn'tบอกbɔ̀ɔksayอย่างนั้นyàang-nánlike that

  I didn't say that.

  This denies the words, not the conversation: something was said, but not this.

• วันนี้wan-níitodayผมpǒmIไปbpaigoไม่ได้mâi-dâican't

  I can't go today.