Text: Particle Ni

The next particle to cover is 'ni'. 'Ni' has many uses, but for the purpose of this tutorial, I will be covering two of them.

The first one is "the goal of movement" or "the goal toward which things move." This is just like the 'e' particle. You can use either one, it does not matter.

きょう、わたしはがっこうにいきます。
Kyou, watashi wa gakkou ni ikimasu.
Today, I will go to school.

–REFRESHER–
Today, I (subject) will be going (movement) to school (place of destination; you are moving to get there).

きのう、わたしはうちにかえりました。
Kinou, watashi wa uchi ni kaerimashita.
Yesterday, I went home.

The second purpose is for time. 'Ni' is used when a /specific/ time or date is being said. However, the particle 'e' CANNOT be used for this purpose. 'E' and 'ni' are only interchangeable with the goal of movement.

–SIDE NOTE–
If someone speaks to you using the particle 'ni' in reference to "goal of movement", you do not have to reply with 'ni' and may use 'e' as well as vice versa.
–END SIDE NOTE–

げつようびにべんきょうします。
Getsuyoubi ni benkyoushimasu.
I (will) study on Monday.

ごぜん八時におきます。
ごせんはちじにおきます。
Gozen hachi ji ni okimasu.
I get up at 8 AM.

ごご十時半にねます。
ごごじゅうじはんにねます。
Gogo juu ji han ni nemasu.
I go to sleep at 10:30 PM.

くがつにかえります。
Kugatsu ni kaerimasu.
I will go back in September.

You would not use 'ni' with time expressions that have to do with the present moment (today, tomorrow), when describing regular intervals (every morning/day/night) or with the word "when."

You would never say:

まいにちにテレビをみます。
Mainichi ni terebi wo mimasu.
I watch TV every day.

Instead, you would say:

まいにちテレビをみます。
Mainichi terebi wo mimasu.

いつかえりましたか。
Itsu kaerimashita ka?
When did you come back?

あしたいきます。
Ashita ikimasu.
I will go tomorrow.

There are some words where it is an option to use the particle. It all depends on the person's preference, style, use of emphasis, etc. Parts of the day (morning, afternoon, night) and the word for "weekend" can use 'ni' or not.

しゅうまつになにをしますか。
Shuumatsu ni nani wo shimasu ka?
What do you do on the weekends?

OR

しゅうまつなにをしますか。
Shuumatsu nani wo shimasu ka?
What do you do on the weekends?

Both of these are correct.