What is the tiny difference between the two sentences?


How should I translate these sentences? It seems that their English
translations are almost the same:

> 窓があきます  
>  窓があいています

And, in a similar instance:

> 電灯がつきます  
>  電灯がついています




The difference is not tiny.

「窓があきます。」 means "The window opens." The window is closed now, but it's going
to open, for example, from now.

「窓があいています。」 means "The window is open." It describes the current state of the
window, not the action of opening.

The difference between 電灯がつきます and 電灯がついています is the same. The former means
"The light will be lit", the latter means "The light is on/lit (now)."

Please check this question for the details of ている: [When is Vている the
continuation of action and when is it the continuation of
state?](https://japanese.stackexchange.com/q/3122/5010) 開【あ】く and 点【つ】く are
usually "change-in-state" verbs.

