nedovoljan

1. insufficient; inadequate
   Plata je nedovoljna za normalan život. — The salary is not enough for a normal life.
   Sud je odbio tužbu zbog nedovoljnih dokaza. — The court dismissed the case due to insufficient evidence.
2. (of a school grade) fail; failing grade
   Dobio sam nedovoljan iz matematike. — I got a fail in maths.

In Serbian schools, "nedovoljan (1)" is the lowest, failing grade.