becciwhitton5094-san,
becciwhitton5094 wrote:She told me that in Japanese the following expressions could all be translated as "have to", "need to" or "must do":
~nai to ikenai
~nakereba naranai
~nakute wa ikenai
~hitsuyou (必要) ga aru
Is that right? I am right in understanding that the difference between these is pretty subtle?
She said that when recommending that someone else do something, you can say ~hou ga ii desu, or ~suru beki da. Is there a difference in nuance between these two expressions?
Basically all you said above is right.
Like I wrote in previous comment, English translation in this level is no longer too helpful
and you need to understand the nuance and usage.
For example, 必要がある has a word 必要 in it, so it's closer to "need to".
Literally, 必要がある means "there's a need".
There's also "speech level", or rather "politeness level", you have to consider. For example, the difference
between "~ hou ga ii desu" and suru beki da" is not just one. The first one ends with "desu" and the latter ends
with "da". Politeness level is completely different. Then, "hou ga ii" literally means "(something) is better"
while the other one is strong recommendation or almost obligation. The expression "suru beki desu/da"
is very strong, so you need to pay attention when and to whom you use.
It doesn't seem very wise to continue explaining quickly because all those expressions need
deeper insights and practice (like you wrote, もっと勉強する必要がある).
Comparing the similar expressions is good to understand the meanings properly, but when it's a comparison
of too many, there's a risk of confusing more or missing something.
(i.e. there was already a confusion of "desu" and "da")
Expressions nakute wa ikenai, nakute wa naranai, etc. need to be studied with more focus.
It seems you have basic idea and understanding of those expressions.
If you have more specific problem in meanings or usage, please feel free to ask us.
Natsuko (奈津子),
Team JapanesePod101.com
