etwas
something
As a pronoun, it refers to an unspecified thing or situation; some thing.
Ich habe im Kühlschrank etwas Leckeres für dich gefunden.
I found something delicious for you in the fridge.

something / somewhat
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something
As a pronoun, it refers to an unspecified thing or situation; some thing.
Ich habe im Kühlschrank etwas Leckeres für dich gefunden.
I found something delicious for you in the fridge.

The word 'etwas' (something/somewhat) is invariable. It is never declined and always keeps the same form, no matter which case it is in.
Ich brauche etwas Zeit.
I need some time.
When 'etwas' (something) is combined with an adjective, the adjective is capitalized and gets the ending for neuter nouns in the singular (-es).
Ich möchte dir etwas Schönes schenken.
I would like to give you something nice.
When 'etwas' (some) stands before a noun to express an unspecified amount, the noun is not declined and remains in the singular. These are usually uncountable things.
Ich habe noch etwas Geld übrig.
I still have some money left.
As an adverb, 'etwas' (somewhat) stands directly before an adjective or another adverb and means 'a little' or 'a bit'. The adjective is then written in lowercase.
Dieser Koffer ist etwas schwer.
This suitcase is somewhat heavy.
nothing
'etwas' and 'nichts' are clear opposites. 'etwas' means an unspecified thing or a small amount. 'nichts' means that no thing is there or that no amount is present. Learners may confuse the words because both often appear without a specific noun. A practical rule is: if at least one thing or a small amount is present, 'etwas' fits. If no thing at all is present, 'nichts' fits.

Für das Projekt brauchen wir noch etwas Geld.
We still need some money for the project.
Nach dem Gespräch sagt sie nichts mehr zu ihrer Kollegin.
After the conversation, she says nothing more to her colleague.