Why the "-es" in phrases like "etwas Nasses"?

Question

I was listening to a German audiobook this morning, and I noticed two phrases:

• etwas Nasses
• etwas Großes

I can't be sure of the capitalization, since I was hearing it, not reading it. They were used to mean "something wet" and "something big", respectively. The two phrases used them in different noun cases (the first was nominative, and the second was either accusative or dative).

Why is it that the adjective gets the -es suffix in cases like this? Is it genitive? Is it nominative and assuming a neuter gender? Is there some other reason?

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Ich habe heute Morgen ein deutsches Hörbuch gehört, und ich habe zwei Ausdrücke bemerkt:

• etwas Nasses
• etwas Großes

Ich weiß nicht, ob die Wörter groß- oder kleingeschrieben werden. Diese Ausdrücke wurden für das Englische "something wet" und "something big" verwendet. Die Sätze hatten verschiedene Fälle, der erste war Nominativ und der zweite entweder Akkusativ oder Dativ.

Warum wird an das Adjektiv in diesem Fall "-es" angehängt?

Answer 1

In the examples you gave we have a nominalized adjective. Per Duden rule 72 these usually need to be capitalized. The gender is not defined by a rule but rather depends on the object, in both cases it is neuter here because the object is either neuter, or it was not defined.

Examples:
Meine Bekannte ist eine Frau
Mein Bekannter ist ein Mann

The case when combined with the pronoun "etwas" will depend enirely on the context

Accusative
Das Große -> Großes, ein Großes ("Wir haben etwas Großes gesehen") Das Nasse -> Nasses ("Wir spüren etwas Nasses")

If we reword the latter to use a dative case the difference becomes obvious:

"Von etwas Nassem reden"

Of course the declination will be different when another gender was used:

"der Nasse" -> gen. "des Nassen": Das Fell des Nassen wurde ganz schwer
"die Große" -> acc. "die Große": Wir haben die Große nach Hause begleitet

Adjectives can be nominalized in both, their non-inflected, and their inflected form.

Answer 2

In German it's called "Substantivierung": An adjective is used as a noun (and written with a capital first letter)

Something like this does also exist in the english language (nominalization), but you don't notice it there because the word doesn't change.

You can find some other examples at wikipedia: link

Answer 3

Like s6robat said, this is "Substantivierung".

When you want to refer to something only by one of its properties, you can use that.

A: Was willst du zum Geburtstag haben?

B: Nur etwas Kleines.

But the same goes for nichts, viel, wenig:

A: Was sagt man so über ihn?

B: Nichts Gutes? / Viel Gutes? / Wenig Gutes?

Like deve pointed out in a comment:

Nouns created from adjectives by appending -e are always neuter:

The -es is because of the accusative, but would be the same in nominative:

A: Etwas Schlimmes ist passiert

The suffix of the substantivated adjective is the same as if you would substitute "etwas [...]" through "[...] Zeug"

Schlimmes Zeug ist passiert

Ich will nur [etwas Kleines / kleines Zeug] zum Geburtstag

See also this guide for adjective declination