Asking a question in Japanese is very simple if you understand the X は Y です sentence structure. You can take almost any sentence like this and turn it into a question simply by adding the question particle か to the end of the sentence.
For example:
これはねこです。(Kore wa neko desu.) This is a cat.
これはねこですか。(Kore wa neko desu ka.) Is this a cat?
The first sentence is a statement in the basic sentence structure form. By adding か to the end of the statement, a question is formed.
か acts as a question mark, so when writing in Japanese you should not place an actual question mark at the end. A period typically follows か even though the sentence is a question. Whenever か is used at the end of a sentence, a Japanese speaker will understand it as a question instead of a statement.
If you want to ask someone a question that doesn’t involve the basic sentence structure, you still use か. For example, if you wanted to ask someone “What time is it?” you would say: なんじですか。Notice です still appears at the end of the sentence with か. This is very common when asking basic questions.
Simple questions often use the word なん orなに, both of which mean “what.” The rule of thumb is that なん is used when “what” appears before です. なん is also used before a noun when counting (such as the earlier example of “What time is it?” じmeans “time”, so なんじ means “what time.”) なに is typically used when “what” appears before a particle.
Here are some examples that use なん.
せんもんはなんですか。(Senmon wa nan desu ka?) What is your major?
せんもんはれきしがくです。(Senmon wa rekishigaku desu.) My major is history.
おなまえはなんですか。(Onamae wa nan desu ka?) What is your name?
ななはらちなつです。(Nanahara Chinatsu desu.) Nanahara Chinatsu.
Notice that in the last statement, only the name of the person was given. The subject (わたしは) was omitted. The subject can often be omitted in many Japanese sentences. This also applies for questions. “I,” “I am,” “You,” and “You are,” are the most frequently omitted subjects from Japanese sentences. Examine the following mini conversations. Notice when the subjects are omitted (shown in parentheses) and when the question particle is used.
A: (あなたは)にほんじんですか。(Anata wa) nihonjin desu ka?
B: はい、(わたしは)にほんじんです。Hai, (watashi wa) nihonjin desu.
A: Are you Japanese?
B: Yes, I am Japanese.
A: (いま)なんじですか。(Ima) nanji desu ka?
B: (いま)いちじです。 (Ima) ichiji desu.
A: What time is it now?
B: It is 1:00.
A: (あなたは)なんねんせいですか。(Anata wa) nan nensei desu ka?
B: (わたしは)さんねんせいです。(Watashi wa) san nensei desu.
A: What year are you? (in college)
B: I am a junior (third year).
A: ふじまるさんはなんさいですか。(Fujimaru-san) nansai desu ka?
B: わたしはじゅうきゅうさいです。(Watashi wa) jyuu kyuu sai desu.
A: Fujimaru-san, how old are you?
B: I am 19 years old.
Keep in mind that you will see か often. When asking a question in Japanese, it can appear after almost any verb.