の・なの

About

The explanatory の can be used at the end of a sentence to indicate a question (i.e. the speaker is seeking an explanation).

E.g. それ、おいしいの？ "Is that tasty?"

When の follows a noun or な-adjective it needs to attach using な.

E.g. 学生がくせいなの？ "Are you a student?"

の can also come at the end of a statement, which is the same explanatory usage. This use of の sounds fairly feminine.

E.g. これ、おいしいの。 "This is tasty." (explanatory; feminine)

Using の to ask a question or form a statement is fairly casual.

Summary

• 

  The explanatory の can come at the end of a sentence to indicate a question or an explanatory statement

• 

  This usage of の is fairly casual