German has no single plural ending. A noun may add -e, -er, -(e)n, -s or nothing at all, and many add an umlaut as well: Buch becomes Bücher, Mann becomes Männer. The plural article is die for every gender, which is the one simplification.
Examples
- Ich habe zwei Brüder und drei Schwestern.
- I have two brothers and three sisters.
- Die Hotels sind voll.
- The hotels are full.
- Zwei Bücher, bitte.
- Two books, please.
The mistake to avoid
The plural is not predictable from the singular - learn it with the noun, like the gender.
Where this fits in
Numbers, days, time, German A1: Count, talk about days and months, give the time, and handle numbers in real situations.