Back-formation from derül or derít, created during the Hungarian language reform, which took place in the 18th–19th centuries.
derű (usually uncountable, plural derűk)
| Inflection (stem in long/high vowel, front rounded harmony) | ||
|---|---|---|
| singular | plural | |
| nominative | derű | derűk |
| accusative | derűt | derűket |
| dative | derűnek | derűknek |
| instrumental | derűvel | derűkkel |
| causal-final | derűért | derűkért |
| translative | derűvé | derűkké |
| terminative | derűig | derűkig |
| essive-formal | derűként | derűkként |
| essive-modal | — | — |
| inessive | derűben | derűkben |
| superessive | derűn | derűkön |
| adessive | derűnél | derűknél |
| illative | derűbe | derűkbe |
| sublative | derűre | derűkre |
| allative | derűhöz | derűkhöz |
| elative | derűből | derűkből |
| delative | derűről | derűkről |
| ablative | derűtől | derűktől |
| non-attributive possessive - singular |
derűé | derűké |
| non-attributive possessive - plural |
derűéi | derűkéi |
| Possessive forms of derű | ||
|---|---|---|
| possessor | single possession | multiple possessions |
| 1st person sing. | derűm | derűim |
| 2nd person sing. | derűd | derűid |
| 3rd person sing. | derűje | derűi |
| 1st person plural | derűnk | derűink |
| 2nd person plural | derűtök | derűitek |
| 3rd person plural | derűjük | derűik |