The question particle か (ka)
Turning a sentence into a question is extremely simple. The Japanese have a question particle "か" (ka) which they place at the end of the sentence to make it a question. The word order in Japanese doesn't change, though the inflection does of course.

In the spoken language か is sometimes dropped. When the question particle か is dropped, the "u" from "-masu" becomes voiced and a question mark is added. The same goes for "desu".

In informal use か is hardly ever used. Men may use it on occasion to sound tough.

Note that when か is used the question mark isn't.
In informal use の is often added, followed by the question mark.

Conjugations: The Mizenkei (未然形)
The mizenkei is used for making negative statements, the causative form, and the passive form. Group 4 verbs change conjugation by changing the last hiragana in the okurigana (送り仮名) from the "u" column to the "a" column. An exception are verbs where the rentaikei ends on う (u), these verbs replace う (u) with わ (wa).

Group 4 conjugations		to write		to buy		to sell		to enter
Rentaikei		書く kaku		買う kau		売る uru		入る hairu
Ren'youkei		書き kaki		買い kai		売り uri		入り hairi
Mizenkei		書か kaka		買わ kawa		売ら ura		入ら haira

The group 2 verbs change conjugation by removing the hiragana る (ru) from the okurigana (送りがな).

Group 2 conjugations		there is/are		to eat		to appear		to see
Rentaikei		いる iru		食べる taberu		出る deru		見る miru
Ren'youkei		い i		食べ tabe		出 de		見 mi
Mizenkei		い i		食べ tabe		出 de		見 mi

Irregular verbs
The irregular verbs する (suru) and 来る (kuru) also have irregular mizenkei conjugations.

Irregular verbs		to do		to come
Rentaikei		する suru		来る kuru
Ren'youkei		し shi		来 ki
Mizenkei		し､せ､さ shi, se, sa		来 ko

Pay special attention to the mizenkei of 来る (kuru). Unlike the ren'youkei which has as pronunciation き (ki), the mizenkei has as pronunciation こ (ko). The mizenkei of する (suru) has three variations, but only し (shi) can be used for the negative. せ (se) and さ (sa) are reserved for the causative form and the passive form.

Negatives
In informal use the verb ない (nai) is added to the mizenkei of the verb.

Positive		Negative
書く	kaku	書かない	kakanai
買う	kau	買わない	kawanai
売る	uru	売らない	uranai
入る ④	hairu	入らない	hairanai
いる	iru	いない	inai
食べる	taberu	食べない	tabenai
出る	deru	出ない	denai
見る	miru	見ない	minai
する	suru	しない	shinai
来る	kuru	来ない	konai

The polite auxiliary verb ます (masu), as well as the verbs ある (aru), である (de aru), and だ (da) have irregular conjugations.

Irregular negatives		polite form
Positive		…ます -masu
Negative		…ません -masen

Irregular negatives		there is/are		to be		to be
Positive		ある aru		である de aru		だ da
Negative		ない nai		ではない de wa nai		じゃない ja nai

じゃ (ja) is a contraction of では (de wa).

です (desu) can be added after ない (nai) to make it polite. Alternatively you can conjugate it to ではありません (de wa arimasen).

Positive		Negative
ある	aru	ない	nai
である	de aru	ではない	de wa nai
だ	da	じゃない	ja nai
あります	arimasu	ありません	arimasen
		ないです	nai desu
書きます	kakimasu	書きません	kakimasen
		書かないです	kakanai desu
食べます	tabemasu	食べません	tabemasen
		食べないです	tabenai desu
来ます	kimasu	来ません	kimasen
		来ないです	konai desu
であります / です	de arimasu / desu	ではありません	de wa arimasen
		ではないです	de wa nai desu
		じゃありません	ja arimasen
		じゃないです	ja nai desu

Yes and no
The Japanese have several words for yes and no. For "yes" はい (hai) and ええ (ee) are polite forms, うん (n) is used among friends. For "no" いいえ (iie) and いえ (ie) are polite, and ううん (nn) is used between friends. The intonation of ううん starts high, drops and then rises again. うん and ううん aren't really words, but more sounds, like the English "uhuh", and "uh-uh".

When replying to a negative question, the Japanese confirm or deny the statement made in the question with yes and no.

Be aware that はい and うん are also used to confirm that someone is listening. It does not necessarily mean that someone is agreeing to what you say.

When giving an answer you should always repeat the main verb, as shown above. Only はい or いいえ is not sufficient.