Meaning of "不了" in "忘不了/喝不了/..."

Question

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!

Answer 1

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

Answer 2

“不了” in this context is pronounced "bu4liao3" and means "to be unable to".

比如说：

吃不了 unable to eat

忘不了 unable to forget

Answer 3

In addition to @Flaudre's answer below, which included this:

吃不了 unable to eat chi bu liao

You can add another 了(this time 'le') to mean 'any more' (or a change of state, from being able to eat to not being able to eat):

我吃不了了 = I can't eat any more. I'm full up. I've had enough. wo chi bu liao le

了 is a great word!