Questions & Answers about Lumea este frumoasă.
Because Romanian usually puts the definite article at the end of the noun.
- lume = world
- lumea = the world
So -a here is the definite article, roughly equivalent to English the. This is a very common Romanian pattern.
Because Romanian adjectives must agree with the noun they describe in gender and number.
Lumea is feminine singular, so the adjective must also be feminine singular:
- masculine singular: frumos
- feminine singular: frumoasă
- masculine plural: frumoși
- feminine plural: frumoase
Even after este, the adjective still agrees with the subject.