Please tell me how to use Japanese 終助詞 の and だ


I've been learning Japanese for a while, but I usually use 敬語, like です、ます, so
I still can not understand how to use something that is not 敬語 correctly,
especially the 終助詞. Like の and だ.

For example, 私は大丈夫 and 私は大丈夫だ. How to use them correctly?

And I now know の can mean a question at the end of a sentence, but sometimes
it does not mean a question, and I don't know what it means when it's not a
question. And what is the difference between の and のだ ?

For example, 猫が好きだ。猫が好きなの。猫が好きなのだ。What is the difference?

Also, I have been told that only woman can use の at the end of a sentence when
it is not a question, but what about man? When man wants to express the exact
same meaning as the one woman says with の at the end of it, what can he use?

For example, how can a man say "猫が好きなの"？

Thank you so much.




### だ

だ is called a copula, roughly translating to the English verb "to be" (is,
are, am, etc.). It is not a particle but a suffix that attaches to the end of
nouns and adjectival nouns (na-adjectives). It is used in informal
conversation, as opposed to its polite counterpart です, which it seems you
already know. Like です, its basic use is to equate two things as equal; in
other words, to say one thing _is_ another thing.

> 私は学生 **だ** - I **am** a student.  
>  彼は大丈夫 **だ** - He **is** all right

As I stated somewhere in the first paragraph, you can only attach it to nouns
and na-adjectives (which are nouns that behave like adjectives). You cannot
attach it to i-adjectives; they stand on their own at the end in informal
speech. This is where だ differs from です, which attaches to i-adjectives.

> × 食べ物はおいしいだ  
>  ○ 食べ物はおいしい

Also unlike です, which only really appears at the end of the main clause, だ
often appears at the end of quotations and subordinate clauses (but not
relative clauses), even if the whole sentence is polite.

> 元気だと言った - He said he was fine.  
>  冬だから客もあまりいません - Because it's winter, there aren't many customers.

The negative of だ is じゃない, which now, just like the negative form of verbs,
conjugates like an i-adjective (so the negative past is じゃなかった, the -て form is
じゃなくて, etc.).

> 私は学生じゃない - I am not a student.  
>  友達じゃない - (He) isn't my friend.  
>  全然好きじゃなかった - (I) didn't like it at all.

Grammatically speaking, だ and じゃない are always required. You can't end a
sentence with a noun.

> × 私は大丈夫  
>  ○ 私は大丈夫だ

However, since it's informal speech, this rule is frequently ignored.

* * *

### の

When used as a sentence-ending particle, の can generally do one of two things
to a sentence, neither of which have the same function as だ. Firstly, it can
emphasize emotion. This usage is used mostly by women or children.

> ブロッコリーが好きじゃないの - I don't like broccoli

Secondly, it can be used as an explanation, or in other words, to fill in an
"information deficit". This の is basically the same thing as のだ/んだ, but with
the だ dropped. See more information about the のだ/んだ construction and meaning
[here](https://japanese.stackexchange.com/a/5399/9749) or
[here](https://japanese.stackexchange.com/a/3685/9749). の as a question marker
applies to this as well- it is the short and informal form of のですか.

> 今は忙しいの - I am busy (as an explanation)  
>  お腹が空いたの - I was hungry (as an explanation)  
>  どこに行くの(ですか) - Where are you going?

It is a little more complicated than that, but the links above should be good
at explaining what の/のだ is used for as opposed to normal statements and
questions.

Note, though, that sentence-ending の must be preceded by な if the preceding
word is a noun so that it can be distinguished from the other uses of の.

> 私のだ - it is mine  
>  私なのだ - it is me (as an explanation).




### だ

だ is called a copula, roughly translating to the English verb "to be" (is,
are, am, etc.). It is not a particle but a suffix that attaches to the end of
nouns and adjectival nouns (na-adjectives). It is used in informal
conversation, as opposed to its polite counterpart です, which it seems you
already know. Like です, its basic use is to equate two things as equal; in
other words, to say one thing _is_ another thing.

> 私は学生 **だ** - I **am** a student.  
>  彼は大丈夫 **だ** - He **is** all right

As I stated somewhere in the first paragraph, you can only attach it to nouns
and na-adjectives (which are nouns that behave like adjectives). You cannot
attach it to i-adjectives; they stand on their own at the end in informal
speech. This is where だ differs from です, which attaches to i-adjectives.

> × 食べ物はおいしいだ  
>  ○ 食べ物はおいしい

Also unlike です, which only really appears at the end of the main clause, だ
often appears at the end of quotations and subordinate clauses (but not
relative clauses), even if the whole sentence is polite.

> 元気だと言った - He said he was fine.  
>  冬だから客もあまりいません - Because it's winter, there aren't many customers.

The negative of だ is じゃない, which now, just like the negative form of verbs,
conjugates like an i-adjective (so the negative past is じゃなかった, the -て form is
じゃなくて, etc.).

> 私は学生じゃない - I am not a student.  
>  友達じゃない - (He) isn't my friend.  
>  全然好きじゃなかった - (I) didn't like it at all.

Grammatically speaking, だ and じゃない are always required. You can't end a
sentence with a noun.

> × 私は大丈夫  
>  ○ 私は大丈夫だ

However, since it's informal speech, this rule is frequently ignored.

* * *

### の

When used as a sentence-ending particle, の can generally do one of two things
to a sentence, neither of which have the same function as だ. Firstly, it can
emphasize emotion. This usage is used mostly by women or children.

> ブロッコリーが好きじゃないの - I don't like broccoli

Secondly, it can be used as an explanation, or in other words, to fill in an
"information deficit". This の is basically the same thing as のだ/んだ, but with
the だ dropped. See more information about the のだ/んだ construction and meaning
[here](https://japanese.stackexchange.com/a/5399/9749) or
[here](https://japanese.stackexchange.com/a/3685/9749). の as a question marker
applies to this as well- it is the short and informal form of のですか.

> 今は忙しいの - I am busy (as an explanation)  
>  お腹が空いたの - I was hungry (as an explanation)  
>  どこに行くの(ですか) - Where are you going?

It is a little more complicated than that, but the links above should be good
at explaining what の/のだ is used for as opposed to normal statements and
questions.

Note, though, that sentence-ending の must be preceded by な if the preceding
word is a noun so that it can be distinguished from the other uses of の.

> 私のだ - it is mine  
>  私なのだ - it is me (as an explanation).

