hi Zi Yang, it somewhat is slightly complicated, however the finest clarification is that German has 3 genders, masculine, female and neuter. (those could memorized - they are no longer logical) you employ Ein for masculine and neuter nouns and eine for female ones. Ein Hut liegt hier (masculine) (A hat lies right here) Eine Katze liegt hier (female) (A cat lies right here) Ein Buch liegt hier (neuter) (A e book lies right here) This works as long because of the fact the nouns (Hut, Buch and Katze) are the priority of the sentence. The e book, the cat and the hat are doing the doing - they are the priority of the sentence (or nominative case.) while the noun turns into an merchandise (recipient of an action) it somewhat is referred to as accusative case and then ein takes endings for masculine nouns. female and neuter nouns stay the comparable: Ich sehe eine Katze (I see a cat) Ich sehe ein Buch (I see a e book) yet Ich sehe einen Hut. (I see a hat) it somewhat is almost cool, because of the fact it means you greater often than not comprehend who's doing what to whom in case you have masculine nouns! Ein Mann beisst einen Hund. is the comparable concept as Einen Hund beisst ein Mann. a guy bites a canines.) The ein shows that it somewhat is the priority (ingredient doing the doing) - a guy (doing the biting). The einen shows that it somewhat is the merchandise (accusative - what the priority acts on) a canines. (being bitten). you won't be ready to do this order reversal in English with out changing the meaning. "a guy bites a canines" has a different meaning in English from "A canines bites a guy!"