Assume Kimberly is calling AAA

AAA: "What can I do for you?"

Kimberly: "my car doesn't start, its engine doesn't work"

Kimberly: "my car won't start, I don't know why"

Are those answers both clear and natural?

I make up the context to understand the difference between "doesn't start" and "won't start". The former indicates Kimberly knows the reason/cause, the latter doesn't.

Is my understanding correct?

2 Answers 2


Most of the time, doesn't and won't are synonymous. But I see two subtle distinctions. First, won't implies being unwilling whereas doesn't implied being unable. My mother doesn't speak Spanish means she is unable, but My mother won't speak Spanish means she can speak Spanish but refuses to do so. Second, won't implies a temporary situation whereas doesn't implies permanent, or semi-permanent. My car won't start unless I put my foot on the brake pedal implies that this is a temporary malfunction, perhaps a problem that only showed up today. But my car doesn't start unless I put my foot on the brake pedal implies that the car is designed that way. It's neither a malfunction nor temporary. It's just a feature that the car has, always had, and always will have.

However, it is certainly possible that even native speakers of English would get these mixed up. If it is unclear from the context whether the speaker meant unable/permanent or unwilling/temporary, the listener would ask for clarification.


Both your sentences mean the same thing and there’s not much difference.

We use will not (or won’t) when we talk about UNWILLINGNESS to do something (e.g. reluctance, refusal):

Mom! John won’t give me back my cookies.

Remember that we can also talk about the refusal of a thing to work in the way it should:

My car won't start, I don't know why.

Similar examples are:

The car keys won’t fit the lock.

The shirt won’t come off.

My car doesn’t start, the engine doesn’t work.

“My car doesn’t start” would imply that there is a mechanical defect in the car. It is often used to mean that something mechanical is broken.

However, both your sentences mean the same thing and can be used interchangeably.

  • Thank you. So the difference is whether the malfunctioning happens repeatedly, right?
    – WXJ96163
    Jun 11, 2020 at 6:45
  • 2
    Using "won't" to describe unwillingness is a "pathetic fallacy". We are figuratively treating the car as if it was a person with wants and a will.
    – James K
    Jun 11, 2020 at 8:21
  • @JamesK Thank you. So, using "won't" is some kind of a figure of speech which is widely acceptable, right?
    – WXJ96163
    Jun 11, 2020 at 10:03

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