"He is a man and she is a woman."
Translation:Er ist ein Mann und sie ist eine Frau.
The word Mann is grammatically masculine, so it requires the masculine indefinite article ein.
The word Frau is grammatically feminine, so it requires the feminine indefinite article eine.
The neuter indefinite article is also ein; you would use it with neuter nouns such as ein Mädchen (a girl).
Note from the last example that the grammatical gender does not necessarily have anything to do with the meaning of the word -- a word can be masculine but refer to an inanimate object, or feminine and refer to a male human, or neuter and refer to a person, etc.
Always learn the grammatical gender together with the word.
I think its because its the same as Spanish ( una/un ) eine is the same as una and ein is the same as un.
Basically, when using a masculine term like Mann, you do not add an "E" because it's reffered to as a female e. You add it to certain words when using feminine terms
Ummmm, I typed the the sentence right, but it shows me that somethings wrong.....