可能【kěnéng】

可能 says something may be so. It goes before the verb, or at the start of the sentence; both are common.

For the future, 可能会 is the usual pair.

"Possible" and "impossible"

可能 is also an adjective. 不可能 is "impossible", 有可能 is "it's possible".

Not for asking permission

English "may I" and "could I" ask permission. 可能 only weighs how likely something is; permission is 可以.

• × 我可能用你的笔吗？ → 我可以用你的笔吗？
• × 你可能帮我吗？ → 你可以帮我吗？

也许 means "perhaps" too and sits in the same places, but it isn't an adjective: there's no 不也许.