das Leid
suffering
Great emotional or physical pain, grief, or misfortune.
Die Flutkatastrophe verursachte unermessliches Leid in der Region.
The flood disaster caused immeasurable suffering in the region.

suffering
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suffering
Great emotional or physical pain, grief, or misfortune.
Die Flutkatastrophe verursachte unermessliches Leid in der Region.
The flood disaster caused immeasurable suffering in the region.

The noun 'das Leid' (suffering) belongs to the word family of the verb 'leiden' (to suffer). Both words describe a state of pain, grief, or misfortune.
Viele Menschen leiden unter den Folgen des Krieges.
Many people are suffering from the consequences of the war.
As a noun, 'Leid' (suffering) is often combined with verbs like 'verursachen' (to cause), 'lindern' (to alleviate), 'ertragen' (to endure), or 'erfahren' (to experience). It often describes a great, severe burden.
Diese Medikamente sollen das Leid der Patienten lindern.
These medications are meant to alleviate the patients' suffering.
In the expression 'leidtun' (to be sorry), the person who feels regret is always in the dative. The fixed structure is: 'Es tut [dative person] leid' (It makes [person] sorry).
Tut es dir nicht leid, was du gesagt hast?
Aren't you sorry about what you said?
In the expression 'etwas leid sein' (to be tired of something), the thing you have had enough of is in the accusative. The person who feels this way is the subject of the sentence.
Ich bin diesen ständigen Lärm leid.
I'm tired of this constant noise.
happiness / luck
'das Glück' and 'das Leid' are clear opposites here. 'Glück' means a state of joy and contentment. 'Leid' means great emotional or physical pain. Both words can talk about strong human feelings and life situations, but in opposite directions: 'Glück' is positive, while 'Leid' is heavy and negative.

Das Leid der Familie nach dem Unfall war groß.
The family's suffering after the accident was great.
Nach vielen schwierigen Jahren fand er endlich sein Glück.
After many difficult years, he finally found happiness.