Questions & Answers about Aceasta este o nebunie.
Both can mean this, but they are not used in exactly the same way.
- aceasta is the fuller, more formal form
- asta is shorter and much more common in everyday speech
So in conversation, many Romanians would naturally say Asta e o nebunie.
The version with aceasta sounds more careful, formal, or written.
Aceasta is the feminine singular form of the demonstrative pronoun.
Acesta is the masculine singular form.
Romanian demonstratives agree in gender and number with the noun they refer to, even if that noun is only implied. So aceasta usually points to something understood as feminine, such as an implied noun like situație or idee.
In very general everyday speech, speakers often avoid this issue by using asta, which is much more neutral in practice.