In Lesson 22 (Dialogue 2 & 4), we learned Ｖた方がいい and Ｖない方がいい forms that express advices ("You had better V" and "You had better not V," respectively). In this lesson, we will learn the obligation form ("You must V"). This form involves double negatives (must NOT NOT V) which create an affirmative meaning (must V) as shown below.

Vなくては (= Vなくちゃ) Vなければ (= Ｖなきゃ)	いけない ならない	must V
If not V	it will not do
書かなくては (= 書かなくちゃ) 書かなければ(= 書かなきゃ)	いけない ならない	I must write it.
見なくては (= 見なくちゃ) 見なければ(= 見なきゃ)	いけない ならない	You must see it.

Ｖなくちゃ is a shortened form of Ｖなくては ("if not V"). Vなきゃ is a shortened form of Vなければ ("provided not V"). To use this obligation form efficiently, practice saying the "must" endings ～なくちゃいけない, ～なきゃならない and other combinations until you can say them without stopping. Then, add a negative stem in front of it as shown:

	negative stem	"must" endings
う-verbs	いか	なくちゃ なくては or なきゃ なければ	いけない ならない	must go
	つかわ			must use
	つくら			must make/cook
	また			must wait
	けさ			must erase/turn off (light)
る-verbs	たべ			must eat
	で			must leave/go out
	おき			must get up
	い			must stay
Irregular	こ			must come
	し			must do

	明日までに、このレポート出(だ)さなくちゃいけないんだ。	I must turn in this report by tomorrow.
	ビールを買う時は、ＩＤがなくてはいけません。	When you buy beer, you must have an ID.
	８時までにオフィスに行っていなきゃならないんです。	I must be/arrive at the office by 8.
	早く行っても、オフィスで待たなければならない。	Even if I go early, I must wait in the office.

Nouns, な-adjectives and い-adjectives can also be used in the same construction to express social necessities or expectations.

	negative stem	"must" endings
Nouns	日本食じゃ	なくちゃ なくて or なきゃ なければ	いけない ならない	must be Japanese foods
	月曜日じゃ			must be Monday
な- adjectives	元気じゃ			must be healthy/energetic
	しずかじゃ			must be quiet
い- adjectives	おもしろく			must be interesting
	小さく			must be small

	オンラインのコースじゃなければいけません。	It must be an online course.
	ぼうねん会(かい)はにぎやかじゃなくちゃいけないね。	The year-end party must be lively.
	図書館はしずかじゃなくてはならない。	The library must be quiet.
	たまごは新しくなくてはなりません。	Eggs must be fresh/new.

Although these forms are interchangeable, ～いけません expresses somewhat stronger and more specific obligations or necessities than ～なりません.

In casual conversations, the last part (いけない or ならない) can be optionally dropped, and this expresses a softer obligation.

	おふろに入らなくちゃ！ or 入らなきゃ！	I/You have to take a bath!
	子どもは元気じゃなくちゃ！ or 元気じゃなきゃ！	Children should be energetic!
	映画はおもしろくなくちゃ！ or おもしろくなきゃ！	Movies should be fun!

This form is related to Vても or Vなくても in the permission form we learned in Lesson 23 (Dialogue 3: おふろに入(はい)ってもいい "you may take a bath").

	Vても	いい	may V (Lit. "Even if V, it's OK.")
Affirmative	飲んでも	いい	You may drink it. (Lit. "Even if you drink it, it's OK.")
Negative	飲まなくても	いい	You don't have to drink it. (Lit. "Even if you don't drink it, it's OK.")

The permission form is commonly used in combination with obligation/necessities forms as shown below.

Verb stem + ながら expresses parallel actions that happen simultaneously by the same person. In the V1ながら, V2 construction, V2 is the main action performed by the subject of the sentence, and V1 is the subordinate action.

The corresponding English construction is "While V2-ing, V1," and the main action is often expressed by V2 ("Don't talk on the cell phone (V1= subordinate action) while driving (V2 = main action)."). However, the main action in English can also be expressed by V1 depending on the context (.e.g, "Let's watch football (V1) while drinking beer (V2)").

If the subjects of two actions are different, ながら cannot be used. This restriction does apply in English.

• ＊兄がテレビを見ながら、私がラジオを聞いた。 [Ungrammatical]
• While my brother watched TV, I listened to the radio. [OK]

Conditional Ｖたら (+ いい) creates a suggestion form "Why don't you V?" (LIt. "It would be good if you V...")

• あそこのATMから、お 金 ( かね ) を 出 ( だ ) したら？
  "Why don't you get the money out of that ATM?"
  
  
• わからなかったら、先生に聞いたらいいですよ。
  "If you don't understand, why don't you ask your teacher?"

V-て + から expresses sequential actions that happen one after another (not necessarily by the same person). In the V1てから, V2 construction ("After V1-ing, V2"), V2 is the main action performed by the subject of the sentence, and V1 is the subordinate action.

The following constraints are applied to this construction.

• V2 must follow immediately after V1 (NOT some time after V1).
  
  
  • 私がここに来てから(かぞえて、)今日でちょうど２０年になります。
    "Since I came here (I have been counting and), it is exactly 20 years today."
    
    
• The timing of V2 is viewed as deliberately controlled by the subject of V2. For this reason, this construction is often used in procedures or directions that involves a sequence of actions.
  
  
  • 問題(もんだい)をよく読んでから、答(こた)えて下さい。
    "Please answer after reading the question carefully."
    
    
  • 火(ひ)をとめてから、カレーを入れて下さい。
    "Put the curry in after turning off the flame/stove."