polite and casual language-- being asked to switch?


So it's been a while that I have been wondering how each level of speech is
called in Japanese. All I have seen, is in textbook the mention of casual,
polite, humble, or honorific speech, but I realized that I have no idea how to
say each in Japanese (not going into slang, dialects or anything). Also, how
can I recognize someone telling me it's okay to be more casual with them
(example of natural sentences I might hear)? Would it be something like
[casual speech]でいいのよ or [casual speech]使っていいよor something more along the lines
of "you don't need to be that polite"? (however you might say that).

Thank you very much.




First of all, linguistically you are not wrong even if you used a less polite
form. However, you are impolite in-terms of culture understandings.  
(@user11589 has already gave you a very good link for reference, so I'm just
going to go simple.)

A simple way to decide which form to use is by the situation and person you
are talking to (similar to dress-code, time/place/occasion a.k.a. TPO).

  * to strangers (even if they are kids better to use) = polite 
  * to shopkeeper/staffs = polite
  * to customer = honorific
  * to people older than you = polite (or honorific)
  * to people who is higher than you in position(work) = honorific (you can transit into polite once you have build a closer relationship)

As you can see by now, most of the time using polite form will be fine.

  * friends (regardless of age) = casual
  * colleagues (position same or lower than you) = casual/polite
  * siblings = casual
  * Family members (older) = polite 
  * Family members (younger) = casual

> Also, how can I recognize someone telling me it's okay to be more casual
> with them (example of natural sentences I might hear)? Would it be something
> like [casual speech]でいいのよ or [casual speech]使っていいよor something more along
> the lines of "you don't need to be that polite"? (however you might say
> that).

As to your question, YES some people do say it. Example： タメでいいよ OR
けいごじゃなくてタメでいいよ。 (you don't need to use honorific/polite, casual is fine)

Note:  
another way to know if you can switch to casual, if you are talking to people
in similar age group and they changed into casual (from polite), you can
change into casual as well.




First of all, linguistically you are not wrong even if you used a less polite
form. However, you are impolite in-terms of culture understandings.  
(@user11589 has already gave you a very good link for reference, so I'm just
going to go simple.)

A simple way to decide which form to use is by the situation and person you
are talking to (similar to dress-code, time/place/occasion a.k.a. TPO).

  * to strangers (even if they are kids better to use) = polite 
  * to shopkeeper/staffs = polite
  * to customer = honorific
  * to people older than you = polite (or honorific)
  * to people who is higher than you in position(work) = honorific (you can transit into polite once you have build a closer relationship)

As you can see by now, most of the time using polite form will be fine.

  * friends (regardless of age) = casual
  * colleagues (position same or lower than you) = casual/polite
  * siblings = casual
  * Family members (older) = polite 
  * Family members (younger) = casual

> Also, how can I recognize someone telling me it's okay to be more casual
> with them (example of natural sentences I might hear)? Would it be something
> like [casual speech]でいいのよ or [casual speech]使っていいよor something more along
> the lines of "you don't need to be that polite"? (however you might say
> that).

As to your question, YES some people do say it. Example： タメでいいよ OR
けいごじゃなくてタメでいいよ。 (you don't need to use honorific/polite, casual is fine)

Note:  
another way to know if you can switch to casual, if you are talking to people
in similar age group and they changed into casual (from polite), you can
change into casual as well.

