If you say that something is probable, you mean that it is likely to be true or likely to happen.
likely
It is probable that the medication will suppress the symptom without treating the condition.
该药物可能治标不治本。
A bomb was the incident's most probable cause.
炸弹很有可能是引起这次事故的原因。
You can use probable to describe a role or function that someone or something is likely to have.
their probable presidential candidate.
他们可能当选总统的候选人。