What is the Difference between だろう and かな and how to use them
It is not hard to understand exactly what both expressions mean by analyzing where they are coming from.
- だろう comes from だ
- だろう is だろ (the 未然 conjugation of だ) + う (助動詞 for 推量 in this case)
The 助動詞 う is not often used for 推量 in everyday speech apart from when it is used with だ (だろう) (or in fixed expressions). Using it may result in you sounding poetic, classical or old school:
This sentence could be written as below in everyday Japanese:
Anyway, I like to see だろう as "must" as in "he must be hungry". It always works and is I think the best way to interpret it (but not always the best translation). It indicates a strong guess/presumption/supposition.
When using it, you kind of "push" your opinion/guess to others, without necessarily expecting a reaction. (that depends on the intonation)
か is what most people would call the "question particle" (it expresses uncertainty). And if we look up な in a dictionary, we get:
Which basically means "Expresses the intention to get the other's consent/reaction, or to remind someone of something".
The two particles combined together indicate that you want to get other's reaction on the question. So it means that you wonder about something, and you want other's opinion about it.
It's translated as "I wonder if..." most of the time.
だろう= Impolite Volitional form of the helper verb だ (is). You know, the form that indicates that something probably is/will be that way, but it's not certain. So it has a feel of things like ''it seems like it's'', ''it probably is'' , ''It'll likely be'', that kinda stuff. Keep in mind in Japanese they use だろう and でしょう more frequently than we use these kinds of phrases.
かな is simply a combination of the sentence ending particles か,and な。 かis used to make things uncertain and at the end of a sentence in a rising tone it's usually like a question mark. They're asking themselves a question, so they're wondering it. な in this context is very similar to ね？, the agreement/confirmation seeker, only you ask it yourself. It's like telling yourself out loud ''It's cold out today huh?''.
The combination ends up meaning ''I wonder if''. Grammatically, かな is put after the main sentence, as they're sentence ending particles. だろう is an ending to the main sentence itself.