아마(a-ma, ama)
An adverb used to express a high-probability guess that something will happen
When to use
high-probability guess, future event prediction, confident expectation
The nuance
아마 is used when the speaker has some confidence in the guess, mainly talking about future events or situations.
혹시(hok-si, hoksi)
An adverb used to express low-probability or hypothetical possibility, or to politely ask or suggest something
When to use
low-probability possibility, polite inquiry, uncertain situation
The nuance
혹시 is used in low-probability or uncertain situations and also adds politeness when asking or suggesting something.