Meaning of "不了" in "忘不了/喝不了/..." I know that 了 after a verb means a completion or termination of a certain action, such as:


  
  吃飽了
  (I am) full.
  開始了
  (It) has started.
  不動了
  (It) is not moving anymore.
  


But what about 了 in 忘不了 and 喝不了? Is 不了 an expression, or does each character have a specific meaning in this context? How would 忘不了 and 喝不了 be translated? (I suppose it would not be I have not forgotten yet and I have not drunk yet...)

Thanks in advance!
了 here is read liǎo which means:


  to finish / to achieve / variant of 瞭｜了 / to understand clearly   -CC-CEDICT


thus 

不了


  unable to / without end -CC-CEDICT


忘不了 = can't forget / unforgettable

喝不了 = can't drink / undrinkable