leuchten
to shine
To emit light or reflect brightly.
Die Laternen leuchten in der Dunkelheit.
The streetlights shine in the darkness.

to shine / to light
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to shine
To emit light or reflect brightly.
Die Laternen leuchten in der Dunkelheit.
The streetlights shine in the darkness.

The verb 'leuchten' (to shine) is closely related to the noun 'das Licht' (light). An object that shines in order to brighten a room is also called 'die Leuchte' (lamp/light fixture).
Diese neue Leuchte über dem Esstisch ist sehr hell.
This new light fixture above the dining table is very bright.
In its basic meaning, 'leuchten' (to shine) is often combined with things that emit light by themselves or reflect it. Typical subjects are stars, the moon, lamps, candles, or screens.
In der klaren Nacht leuchteten die Sterne am Himmel.
On the clear night, the stars shone in the sky.
In its figurative meaning, 'leuchten' (to shine) is used almost exclusively in connection with 'Augen' (eyes). It describes an expression of strong, positive feelings such as joy, enthusiasm, or love.
Als sie von ihrer Reise erzählte, leuchteten ihre Augen vor Begeisterung.
When she talked about her trip, her eyes shone with enthusiasm.
When 'leuchten' means to direct light at something, it is usually followed by a preposition with the accusative that indicates direction. Typical prepositions are 'in' (into), 'auf' (onto), or 'unter' (under).
Er leuchtete mit der Taschenlampe unter das Bett, um seine Socken zu finden.
He shone the flashlight under the bed to find his socks.
to shine / seem
'scheinen' and 'leuchten' can both mean that light is visible. 'scheinen' is often used for the sun, moon, or light falling somewhere: 'Die Sonne scheint ins Zimmer' (The sun is shining into the room). 'leuchten' emphasizes more strongly that something is bright or gives off light itself, for example a lamp, a sign, or a screen. Learners may confuse the words because both have to do with light. As a simple guide: 'Die Sonne scheint' (The sun is shining), 'eine Lampe leuchtet' (a lamp is shining / lit).

Im Flur leuchtet die kleine Lampe die ganze Nacht.
In the hallway, the small lamp stays on all night.
Am Morgen scheint die Sonne direkt in die Küche.
In the morning, the sun shines directly into the kitchen.