Learn Hardcore German: Das Licht scheint durch das Fenster.

In German, every noun has a fixed grammatical gender. Licht happens to be neuter, so it always takes the article das in the singular: das Licht. This is something you largely have to memorize, often together with the noun (for example: das Licht, die Lampe, der Scheinwerfer).

Why is there also das in das Fenster?

Fenster is also a neuter noun in German, so it uses the same article das in the singular: das Fenster. The fact that both nouns take das is just coincidence; they are both neuter. Not all nouns ending in -er are neuter, but Fenster is.

Why is the verb scheint and not scheinen here?

The infinitive (dictionary form) is scheinen. In the present tense, for er/sie/es (third person singular), it is conjugated as scheint. Since das Licht is singular (like es), the correct form is scheint: Das Licht scheint ….

In English we say The light is shining. Why is it just scheint and not something like ist scheinend?

German usually uses the simple present to express both shines and is shining in English. So Das Licht scheint can mean The light shines or The light is shining, depending on context. The form ist scheinend is grammatically possible but sounds unnatural here; Germans almost never form a progressive tense this way in normal speech.

Why is it durch das Fenster and not durch dem Fenster?

The preposition durch always takes the accusative case in German. The accusative form of the neuter article is das, not dem. Dem is dative. So the correct phrase is durch das Fenster (accusative), meaning the light is going through the window.

Can I also say Durch das Fenster scheint das Licht? Is that still correct?

Yes, that is perfectly correct. German word order is flexible as long as the conjugated verb is in second position in a main clause. In Durch das Fenster scheint das Licht, the phrase Durch das Fenster counts as the first element, and scheint is still in second position, so the sentence is grammatically fine. It just puts a bit more emphasis on the window.

What is the difference between scheinen and leuchten? Could I say Das Licht leuchtet durch das Fenster?

Scheinen is usually used for light sources or light itself emitting or appearing (the sun shines, the light shines). Leuchten means to shine, to glow, to give off light, often with a nuance of glowing or being bright in itself (a lamp glows, eyes glow).
Das Licht leuchtet durch das Fenster is understandable but sounds slightly odd, because the light itself is the thing that is already emitted; we usually say Das Licht scheint durch das Fenster or Die Lampe leuchtet.

Why are Licht and Fenster capitalized?

In German, all nouns are capitalized, regardless of their position in the sentence. Since Licht and Fenster are nouns, they must start with capital letters: Licht, Fenster. This is a standard spelling rule, not emphasis.

Is scheint durch a separable verb, like durchscheinen?

No. In this sentence, scheint is the main verb, and durch is a preposition that belongs with das Fenster (durch das Fenster).
There is a separable verb durchscheinen (to shine through), where you could say Das Licht scheint durch. That is a different structure: durch in that case is a separable prefix of the verb, not a preposition.

Could I drop the article and say Licht scheint durch das Fenster?

You might see Licht scheint … in poetic or very stylistic language, but in normal standard German you usually use the article: Das Licht scheint durch das Fenster. Dropping the article sounds more like a headline or a fragment than a regular sentence. For everyday use, keep das.

How do you pronounce ch in Licht and durch?

The ch in Licht is a soft, front sound, often called the ich‑Laut, made with the tongue near the hard palate (similar to the h in English hue, but stronger and hissier).
In durch, many speakers use a sound closer to the ich‑Laut too, but some use a slightly more dark/back variant (between the ich‑Laut and the Bach sound). It is never pronounced like the ch in English chair.

Why not say im Fenster or aus dem Fenster instead of durch das Fenster?

Each preposition changes the meaning:

durch das Fenster = through the window (the light passes from outside to inside, or vice versa).
im Fenster = in the window (for example, a lamp or a decoration that is sitting in the window area).
aus dem Fenster = out of the window (for example, someone is looking or throwing something out of the window).

For the idea that light passes from one side to the other, durch das Fenster is the natural choice.