manjak

1. (+ gen.) lack; shortage
   Stalno sam umoran zbog manjka sna. — I'm always tired from lack of sleep.
   Bolnice imaju veliki manjak medicinskih sestara. — Hospitals have a serious shortage of nurses.
2. (of money) deficit; shortfall
   Na kraju smene u kasi je bio manjak od dve hiljade dinara. — At the end of the shift the till was two thousand dinars short.

What is lacking goes in the genitive: manjak vremena, manjak novca.