What does it mean word for word?
The phrase 気は確かですか？ literally asks if one's spirit or mind is certain or reliable.
Which one should you use?
While 気は確かですか？ is a standard way to phrase the question, other forms exist depending on the intensity and social context. For example, 頭おかしいんじゃない？ and マジで頭おかしいんじゃないの？ are informal ways to express the sentiment. If you want to be more blunt, aggressive or informal, you might use 狂ってるのか？ For a more common way to express this sentiment in a polite but confrontational manner, use 頭がおかしいんじゃないですか？
Is there a formal and an informal way to say it?
The level of politeness varies significantly between forms. 頭がおかしいんじゃないですか？ is also polite but carries a confrontational tone. In contrast, 頭おかしいんじゃない？, マジで頭おかしいんじゃないの？ and 狂ってるのか？ are informal. Specifically, 狂ってるのか？ is very blunt and aggressive.
How do you pronounce it?
ki wa tashika desu ka?
Did you know?
- The word 狂う (kuruu), found in the aggressive 狂ってるのか？, is also the standard verb used to describe a clock that has lost its rhythm or a machine that has malfunctioned.
- Using the polite form ですか in 頭がおかしいんじゃないですか？ does not make the phrase friendly. It creates a 'polite distance' that can actually make the insult feel colder and more biting.
- While 'crazy' in English can sometimes be used as a lighthearted compliment for a wild person, using the Japanese equivalent 頭おかしい is almost always perceived as a genuine insult to one's intelligence or sanity.
Example conversation
Kenta suggests spending all their savings on a lottery ticket.
- 健太 Kenta全部宝くじに使いましょう！zenbu takarakuji ni tsukaimashō!Let's spend it all on lottery tickets!
- 美咲 Misakiえっ、気は確かですか？e, ki wa tashika desu ka?What, are you crazy?
- 健太 Kenta当たったら最高ですよ。atattara saikō desu yo.It would be great if we won.
- 美咲 Misaki無理な話です。muri na hanashi desu.That's impossible.
