This is often done with people or abstract things (things you can't touch).
They are really nouns but are declined like adjectives. And since it is a noun, it must be capitalized.
- „Ein fremder Mann klingelt an der Tür.“ = „Ein Fremder klingelt an der Tür.“ // "A stranger is at the door."
- „Ein obdachloser Mensch schläft auf der Straße.“ = „Ein Obdachloser schläft auf der Straße.“ // "A homeless (man) sleeps on the street."
Turning Adjectives into Nouns
Normal sentence: Article + Adjective/Participle + Noun
- „Sandra hat schon wieder einen neuen Freund.“ // "Sandra has a new boyfriend again."
When the noun is obvious, we can simply remove the noun and capitalize the adjective/participle (since it's now a noun!)
- „Sandra hat schon wieder einen Neuen.“
In this case (because of the context of the situation), "Freund" is obvious and can therefore be left out. The adjective "neuen" becomes a noun and is capitalized. But we still have to keep the adjective ending.
Nouns that are often obvious and therefore left out include "Mensch," "Mann," and "Frau."
Adjectives as Nouns
Participles as Nouns
Participles are often used as adjectives. Just like other adjectives, we can remove the noun (if it’s obvious) and turn the participle into a noun by itself.
- „Beim Flugzeugabsturz gab es keine Überlebenden.“ // "There were no survivors of the plane crash."
- „Der Vermisste konnte noch nicht gefunden werden.“ // "The missing one couldn't be found yet."
All of the endings in these examples are in the nominative case. If the noun is in a different case, it would have a different ending.
- When adjectives or participles are used as nouns, the original noun (normally words like "Mann," "Frau," "Mensch") is left out because it is obvious or universally known.
- The adjective stays but is still declined based on the article and case. Since it is now grammatically a noun, it must be capitalized.
An overview of what you have to pay attention to when dealing with adjectives in general.
A detailed explanation of the rules for Adjective Declension.
A simple step-by-step guide for finding the right adjective ending: Adjective Declension: 4-Step Rule.
Adjective declension depends on whether there is a definite article, indefinite article (including possessive determiners or the negative article), or no article at all (the zero article) in front of the adjective.
You have to know the gender of the noun.