I'm learning how to decline adjectives. And I stumbled on this sentence.
Wir brauchen dringend Hilfe.
Can someone please tell me why dringend is not declined to dringende? Since Hilfe is accusative and feminine, I thought it would be dringende.
As mentioned in a comment, it's used as an adverb. It'd be more clear if the sentence read:
Dringend brauchen wir Hilfe.
That being said, your assumption isn't wrong either.
Wir brauchen dringende Hilfe.
In that case dringende is the adjective that describes the noun.
It's just more common here to use the adverb to describe urgency rather than using an adjective.
"Since Hilfe is accusative and feminine," you would be right about dringende if it were used as an adjective to modify Hilfe. So your idea is not wrong with regard to the declension of an adjective, as phrased.
The more common usage, however, is to use an adverb to modify brauchen. Then the correct form is dringend.
Em1 made this point when he said that "It'd be more clear if the sentence read:
'Dringend brauchen wir Hilfe.'"
This puts dringend before the verb. But it can also go after the verb.
Your version has dringende preceding the noun that it would modify.