どうしてWhy

どうして is a polite and versatile way to ask 'why' in Japanese. It can carry a feeling of wanting to know the process or story behind something, literally coming from どう 'how' and して (the て form of する, 'to do'). It is like asking 'how did it come to be that (A)?', and can sometimes express curiosity or surprise.

Of the three common ways to say 'why' in Japanese, どうして is the most neutral, with なぜ being more formal and なんで being more casual.

Caution

Be careful not to confuse どうして with the similar sounding phrase どうした. While どうして asks 'why?', どうした is used to show concern and ask 'what's wrong?' or 'what happened?'. どうした will often be followed by の, and the polite form どうしましたか may also be seen.