What are good words to use for "probably"?

Question

I understand that there are a variety of ways to say "probably," which depend on the context (my attempt at translation in parentheses):

вероятно (a bit literary, more in reference to likelihood)
наверно (more colloquial than above)
возможно (more in reference to a possibility)
скорее всего (implying something of the highest likelihood)
может быть (maybe, could be, can be)
пожалуй (seems more casual)

As a non-native speaker, should I default to using some of these words over others? Are these generally interchangeable, or is it confusing if one is said instead of another? Basically, it's hard for me to tell which is best to use in different contexts.

Answer 1

These are all generally interchangeable. That said, you can divide them into groups:

"Colloquial" (наверно/наверное, может быть), which are mostly used in day-to-day speech (closer to "I guess" and "I think so");

"Formal" (вероятно, пожалуй), rarely used in speech, but often seen in articles (вероятно is more scientific, closer to "probably", and пожалуй is something you'd see in literature rather than hear in speech);

"In-between" (возможно, скорее всего) - возможно is quite close to "possibly", and скорее всего would be close to "It is likely that...", which you'd see in news.

Using these in a "correct" manner would require a lot of experience, so even if you use вероятно in a place where наверно would make more sense, you will simply sound more foreign - people will have no issue with understanding you.

Answer 2

Basically, it's hard for me to tell which is best to use in different contexts.

If you are almost sure, use скорее всего.

If you are not that sure, but chances are much higher than 50%, use вероятно (more formal) or наверное (less formal).

If you don't know if something is true, but it is possible, use возможно (more formal) or может быть (less formal).

Don't use пожалуй, as it has a special meaning.

Don't use the spelling наверно, since наверное is better. Наверно instead of наверное is like definately instead of definitely.