Volition is the speaker's will to do or not do something. In Japanese, there are both affirmative and negative volitional forms. For starters, we will learn about the endings used to create affirmative volitional statements.
As far as meaning is concerned, the affirmative volitional form either translates as "let's" or "I will." If the statement implies participation from others, then the former interpretation is intended. If the statement doesn't imply the participation of others, then the latter interpretation is intended.
Although verbs aren't the only things that have volitional forms, we will limit our discussion to verbal volitional phrases for now. In plain speech, there are two auxiliary verbs used to create the affirmative volitional form: ～よう & ～う. The only difference between ～よう and ～う is what class of verbs they're used with.
|/iru/-Ending Ichidan Verbs||見る + よう →||見よう||Let's/I'll see|
|/eru/-Ending Ichidan Verbs||食べる + よう →||食べよう||Let's/I'll eat|
|/u/-Ending Godan Verbs||買う + う →||買おう||Let's/I'll buy|
|/ku/-Ending Godan Verbs||書く + う →||書こう||Let's/I'll write|
|/gu/-Ending Godan Verbs||泳ぐ + う →||泳ごう||Let's/I'll swim|
|/su/-Ending Godan Verbs||話す + う →||話そう||Let's/I'll talk|
|/tsu/-Ending Godan Verbs||勝つ + う →||勝とう||Let's/I'll win|
|/nu/-Ending Godan Verbs||死ぬ + う →||死のう||Let's/I shall die|
|/mu/-Ending Godan Verbs||読む + う →||読もう||Let's/I'll read|
|/ru/-Ending Godan Verbs||図る + う →||図ろう||Let's/I'll devise|
|Suru Verbs||する + よう →||しよう||Let's/I'll do|
|Kuru||来る + よう →||来（こ）よう||Let's/I'll come|
Translation Note: In English, it is not always the case that "I will" is the best phrasing to indicate personal volition to do something, especially since it also functions as the future tense auxiliary. Whenever this is the case, "shall" can be a better working translation of the affirmative volitional auxiliaries of Japanese.
Pronunciation Note: In casual speech, the final う at the end of these forms may be heard omitted.
The main usage of these endings is to express one's volition/will to do something. This is referred to as the 意志形 in Japanese. This is either used in a sense of including those around you or simply used to solely indicate one's own intention.
I'll eat sushi/Let's eat sushi.
Let's get this (much) straight.
How about taking a rest for a while?
It's not that we have to make it on time. So, let's go slowly.
Word Note: 間に合う should only be used with time.
You're going to eat on top of this?
Why don't we go out?
How about I/we study Chinese?
Let's go outside after we finish dinner.
Since this train is crowded, let's get on the next one.
Determination/Volition of Others
～（よ）うと思います shows that oneself is now determined to do something. In contrast, ～（よ）うと思っています either shows that oneself has made the decision to do something some time ago or the volition of others.
My older sister is thinking about teaching Japanese in China.
I think I'm going to Hawaii.
I'm considering receiving scholarship money.
I'm thinking of becoming a movie director in the future.
Likelihood (Old-Fashioned Speech)
A meaning that has fallen out of use but is still seen in old-fashioned speech and literature is the ability to show likelihood. This has largely been replaced with のだろう, which combines だ and ～う, as we will see again later in this lesson. Though this meaning is largely defunct, it can be distinguished from the others by not just differences in tone but also by context. This meaning of the volitional endings involves statements about state, not an action in which the speaker has control over.
You're also probably starving because you've been walking for so long.
They'll probably be able to point it out.
There are some grammatical instances where this meaning of the volitional endings lives on in modern language use. These instances include the patterns ～（よ）うはずがない and （よ）うものなら.
Such a thing should not happen.
If you are to remain quiet, you will end yourself.
Another usage of these endings is making rhetorical questions when followed by the rhetorical question-marker か. In this situation, か has a sharp drop in pitch. This usage has largely been replaced by ～のだろうか, which incidentally also uses the auxiliary ～う.
Will [I/you/he/she/it] really be forgiven?
Can he really do that?
Even if run away, you don't have any money.
Whether it's true or a lie, I still have no part in it.
Even if you go or don't go, it's my victory.
No matter how much it's protested against, the consumer tax hike will be enforced.
No matter the suffering I suffer, I won't want to change what I've decided.
No matter how much money I lose, I'll continue to gamble.
Whatever you do, it's nothing that I know.
I play football even if it rains.
I will support them no matter how long it takes.
Should you ever have the nerve to talk back to the teacher, you'll surely get scolded severely.
It would be grave should there be a fire.
Just About To...
～（よ）うとしたら is when "just as one is about to do X, Y happens". Y is out of your control, and often includes speech modals like ～てしまった and ～きた.
I was about to get on the train when the door (regrettably/accidentally) closed.
When I tried to eat the ice cream I bought while walked, I was scolded and told that it was "indecent".
Just as I was about to go to the coffee shop, it started to rain.
Just as I was going to leave, a phone call came.
The polite speech equivalent of both ～よう and ～う is ～ましょう. Conjugating with this is the same as with ～ます. In fact, this is just a combination of ～ます + ～う! Meaning-wise, it is not used in all sorts of grammar patterns like its plain speech counterparts. Instead, it is limited to showing "let's" or "I will/shall." Very rarely is it used to show likelihood, in which case it behaves just like its plain speech counterparts.
|/iru/-Ending Ichidan Verbs||見る + ましょう →||見ましょう||Let's/I'll see|
|/eru/-Ending Ichidan Verbs||食べる + ましょう →||食べましょう||Let's/I'll eat|
|/u/-Ending Godan Verbs||買う + ましょう →||買いましょう||Let's/I'll buy|
|/ku/-Ending Godan Verbs||書く + ましょう →||書きましょう||Let's/I'll write|
|/gu/-Ending Godan Verbs||泳ぐ + ましょう →||泳ぎましょう||Let's/I'll swim|
|/su/-Ending Godan Verbs||話す + ましょう →||話しましょう||Let's/I'll talk|
|/tsu/-Ending Godan Verbs||勝つ + ましょう →||勝ちましょう||Let's/I'll win|
|/nu/-Ending Godan Verbs||死ぬ + ましょう →||死にましょう||Let's/I shall die|
|/mu/-Ending Godan Verbs||読む + ましょう →||読みましょう||Let's/I'll read|
|/ru/-Ending Godan Verbs||図る + ましょう →||図りましょう||Let's/I'll devise|
|Suru Verbs||する + ましょう →||しましょう||Let's/I'll do|
|Kuru||来る + ましょう →||来（き）ましょう||Let's/I'll come|
Pronunciation Note: Though less polite, the final う in these forms can be heard omitted. It is also possible to hear the しょ pronounced as ひょ in certain dialects, especially traditional Kyoto Dialect speech.
In lowering prices in order to boost sales, let's knock off 2000 yen from the price.
Shall I call?
Particle Note: This usage of から may be replaced with が.
Let's go out to eat together.
Let's head out at once!
Let's do our best to live in this world as much as possible.
Phrase Note: 世にある means "to live in this world".
～だろう comes from the volitional form of だ. It is often shortened to ～だろ. ～だろう is often not used by females due to the brisk tone it often gives.
1. Used to show guess. It may follow nouns, adjectives, and verbs.
It will probably rain tomorrow.
It will surely get worse.
There will be no more than ten attendees.
Based on that condition, divorce is surely close.
It's probably a bother.
2. ～だろうか may be used to express personal doubt, especially in one's inner monologue. This is the case for both men and women, and in this sense, it can be translated as "I wonder..." In the spoken language when paired with a rising intonation, it can be used to direct serious doubt at someone about something or that individual.
I wonder what time it is.
I wonder when he'll carry it out.
Who would go to the Diet?
How would such a stupid action be allowed?
Isn't he supposed the criminal?
Aren't you coming too?
Grammar Note: When the particle か is dropped like in Ex. 51, the speaker is strongly seeking affirmation from the listener.
3. "...だろうが" and "...だろうと" show supposition and mean "even (in/as)" or "no matter". The former is used in the sense of "even as" whereas the latter is used in the sense of "even in/no matter."
I plan to carry it out even in rainy weather
Even as children, they don't show mercy.
No matter what kind of person you are, you can enjoy this movie.
4. ～だろうに means "even though it's supposed to be". When seen at the end of a sentence, it is often translated as "how I wish!"
Even though it was supposed to be painful, he persevered well.
How I wish I could live my life again!
If we only left a little bit more early, we would have made it on time.
For the most part, ～でしょう is the polite form of ～だろう. ～でしょう comes from the combination of です and ～う. It is often shortened to ～でしょ in casual speech. It has largely replaced だろう whenever it isn't followed by some particle. However, it is possible to see ～でしょうに.
It's probably snow this evening.
It'll probably return.
Headache should subside with medicine.
Will this be alright?
I think it'll probably make her really happy.
Are we not going to be able to make it?
～でしょうか normally goes after the plain form, but it's occasionally after ～ます in attempts to be more honorific.
How many years has it been since you've come to Japan?
Do you understand?