die Leuchte
light
A device that produces light; a lamp including its socket, light source, and shade.
Wir haben eine neue Leuchte über dem Esstisch montiert.
We installed a new light above the dining table.

light / luminary
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light
A device that produces light; a lamp including its socket, light source, and shade.
Wir haben eine neue Leuchte über dem Esstisch montiert.
We installed a new light above the dining table.

The noun 'die Leuchte' (the light/luminary) is derived directly from the verb 'leuchten' (to shine, to emit light). So a Leuchte is literally 'something that shines'.
Die Sterne leuchten heute Nacht besonders hell.
The stars are shining especially brightly tonight.
You can recognize the figurative meaning by the fact that a person is being discussed. It is usually mentioned in connection with a field of expertise, often with the phrase 'eine Leuchte auf dem Gebiet ... sein/gelten' (to be/be considered a luminary in the field of ...).
Professor Schmidt ist eine anerkannte Leuchte in der Genforschung.
Professor Schmidt is a recognized luminary in genetic research.
In connection with the physical object, verbs such as 'eine Leuchte anbringen' (to install a light), 'eine Leuchte montieren' (to mount/install a light), or 'eine Leuchte einschalten/ausschalten' (to switch a light on/off) are often used.
Kannst du bitte die Leuchte im Flur ausschalten?
Could you please switch off the light in the hallway?
Calling a person a 'Leuchte' (luminary) is rather elevated or educated language. It is often used approvingly, or sometimes slightly ironically.
Er hält sich für eine große Leuchte, aber seine Ideen sind nicht neu.
He thinks he's a great luminary, but his ideas aren't new.
light
'das Licht' and 'die Leuchte' can both mean a device that makes things bright. 'Licht' is very general in everyday language and can also simply mean the brightness. 'Leuchte' refers more precisely to the device, for example a 'Deckenleuchte' (ceiling light) or 'Schreibtischleuchte' (desk light). In addition, both words can figuratively mean an especially capable person, a luminary. This meaning often sounds somewhat elevated or joking with 'Leuchte', while with 'Licht' it mostly appears in fixed expressions. The words can be confused because both occur in the area of lighting and also figuratively for intelligent people. In practical terms: for brightness, say 'Licht'; for the device, 'Leuchte' is often more precise.

Sarah sucht eine neue Leuchte für den Schreibtisch, weil die alte kaputt ist.
Sarah is looking for a new light for the desk because the old one is broken.
Ich mache das Licht an, damit wir die Unterlagen besser lesen können.
I'll turn on the light so we can read the documents better.