This is the 1133rd most frequent German word.
a
The German word "a" does not exist as a standalone word; it may refer to the letter "a" or appear in contexts like abbreviations.
The word 'ein' here denotes an indefinite article for a singular noun, 'Buch,' in the accusative case.
Ich habe ein Buch gelesen.
I have read a book.
'Eine' is an indefinite article for the singular feminine noun 'Katze,' used as the nominative subject of the sentence.
Eine Katze sitzt auf dem Baum.
A cat is sitting on the tree.
'Ein' is used as an indefinite article for the singular neuter noun 'Auto,' applied in the accusative case.