This is the 4271st most frequent German word.
ein
"Ein" means "a" or "one" in English.
In this sentence, 'ein' is used as an indefinite article for the neuter noun 'Auto', which indicates an unspecified car.
Ich sehe ein Auto.
I see a car.
Here, 'ein' serves as an indefinite article for the masculine noun 'Tag', signifying a non-specific, beautiful day.
Es war ein schöner Tag.
It was a beautiful day.
In this context, 'ein' acts as an indefinite article associated with the neuter noun 'Stück', referring to an unspecified piece of cake.