Difference between the words «почему» and «зачем»

The most curious students’ as well as my favorite topic is a notional difference between analogous and sometimes at first sight even similar words and expressions.

Even foreigners who know the Russian language pretty well often fail in the usage of words which resemble typical synonyms but in fact have different meanings especially with context. One of the most common cases is the usage of the word «почему» [pachimu] instead of «зачем» [zachem]. If you make such mistake, don’t worry – it’s quite natural because outside the context these two words have quite similar meaning. They are also similar to the English word «why» which combines all the meanings of Russian «почему» [pachimu], «зачем» [zachem] and even «а что» [a chto].

Почему ты сегодня такой грустный? - Why are you so sad today?
Зачем мы пришли в это кошмарное место? - Why we have come to this terrible place?

Ты замужем? - Are you married?
Нет. А что? - No. Why?

Sometimes there can be misunderstanding because the students who just begin learning the Russian language often make a loan translation of the word in the context using its accidental meaning. Imagine the situation. I want to send you a movie tutorial but don’t know whether you can watch it and have technical equipment or not. Then I decide to ask the question and we have the following dialogue:

- У вас есть видеоплеер на компьютере? - Do you have video player on your computer?
- Да. Почему? - Yes. Why?

or

- У вас есть видеоплеер на компьютере? - Do you have video player on your computer?
- Да. А почему? - Yes. But why?

In the first case you definitely wanted to say «Да. А что?» [Da. A chto?], in the second – «Да. А зачем?» [Da. A zachem?].

I ask you whether your computer has video player or not, so you become interested in this question – why it should have this software. But the meaning of your counter question gets distorted because you have used the word «почему». To be precise, your question sounds quite unnaturally. In this case the word «почему» is used instead of the word «зачем» but it didn’t replace its meaning.

So how can we understand, when to use the word «зачем» and when the word «почему»? Let’s examine.

Before to ask question you should understand what you mean: purpose or reason of an action.

You can replace the question «зачем» with the following interrogative sentences: «с какой целью?», (for what purpose?), «для какой цели?» (wherefore?), «для чего?» (what for?).
The word «почему» can be replaced with the interrogative sentences: «что к этому привело?» (what have led to this?), «что вас заставило это сделать/так подумать?» (what made you do so/think this way?).

Thus, when during our short dialogue you want to find out why you need video player, it’s clear that you mean: «for what purpose do I need it?», «wherefore do I need it?».

Let’s try to use these questions. Then our dialogue can be as follows:

- На вашем компьютере есть видеоплеер? - Do you have video player on your computer?
- Да. Почему вы спрашиваете? - Yes. Why are you asking?

The word «почему» is used in this sentence absolutely right because the interrogative sentence «почему вы спрашиваете?» (why are you asking?) has the similar meaning as «что вас заставило задать этот вопрос?» (what made you ask this question?) – Last expression sounds too formal and strictly but it doesn’t matter because our goal now is to feel the difference.

The Russian language can’t exist without exceptions – that’s why there are some cases when the word «зачем» is used within the meaning of «почему». This form is uncommon and considered to be archaic but you can meet it, for example, in literary texts and poetry. Such phrases sound more poetically and emotionally then everyday speech. For example, «Зачем я не птица?..» (Why am I not a bird?...)

A speaker does not ask, for what purpose was he/she born as a human being, but asks with a note of regret – why, for what reason he is not able to fly in the sky and feel himself more free.

Well, let’s sum it up with the simple formula:

Зачем = Purpose
Почему = Reason