I’ve always wonder what is the difference between the word 可能 and 能. I know it both means can, possible but is there any difference between them?
Often 能 is used where "capability" takes on a practical sense (not necessarily about being physically able to do something). Typically, 可能 is used when deciding if something is a suitable thing to do.
We do the same thing in English: I can swim (capability) vs. I can swim in Summer (possibility).
能 and 不能
Wǒ néng yóuyǒng.
I am capable of swimming.
This literally implies I am physically capable of swimming. It doesn't express whether or not I want to go swimming, if I'm allowed to go swimming, and if swimming is a suitable activity (although some of this will be clear from context).
A example where 能 describes a literal capability is:
Luōgēn bùshì tā de zhēnmíng, bìngqiě hái bùnéng yóuyǒng.
Logan is not his real name, and he cannot swim.
An example where 能 describes a practical capability is:
Dài yǐnxíng yǎnjìng néng yóuyǒng ma?
[If someone] wears contact lenses, can they go swimming?
Of course, wearing contact lenses has no effect on one's ability to swim.
可能 and 不可能
Nǐ kěnéng yóuyǒng.
You could possibly go swimming.
This indicates the possibility of going swimming; the person we're saying this to may or may not be able to swim. An actual example is:
Nǐ kěnéng yóuyǒng huòzhě qí zìxíngchē
You could go swimming or ride a bike
Another example is:
Chūnjié qíjiān de shuǐwēn bǐjiào dī, wǒ juédé bù kěnéng yóuyǒng
During Spring Festival, the water temperature is comparatively low, I feel it is not possible to go swimming.
In this example, we could change 不可能游泳 to 不能游泳 to talk about a practical impossibility.
Note: I'm a Chinese learner too. I tried to ensure this is correct, but please let me know if I've made a mistake I'm unaware of.
So you're right about 能. MDBG defines it as:
can / to be able to / might possibly / ability / (physics) energy
But, 可能 on the other hand has a different set of meanings: MDBG defines it as:
might (happen) / possible / probable / possibility / probability / maybe / perhaps / CL: 個｜个
- 能 = able
- 可能 = maybe
Here's two examples using 去 (go):
你明天能去吗？ Are you able to go tomorrow?
他可能去也可能不去。 He might go and then again he might not.