undankbar
ungrateful
Showing no gratitude for help, kindness, or gifts.
Er war so undankbar und hat sich nicht einmal für das teure Geschenk bedankt.
He was so ungrateful and didn't even say thank you for the expensive gift.

ungrateful
Loading your saved state.
ungrateful
Showing no gratitude for help, kindness, or gifts.
Er war so undankbar und hat sich nicht einmal für das teure Geschenk bedankt.
He was so ungrateful and didn't even say thank you for the expensive gift.

The word is made up of the prefix 'un-' and the adjective 'dankbar' (grateful). The prefix 'un-' negates the base word, so it means 'not grateful.'
Es ist enttäuschend, wenn Menschen undankbar sind.
It is disappointing when people are ungrateful.
The meaning changes depending on what is being described. If 'undankbar' refers to a person, it means 'not grateful.' If it refers to a task or job, it means 'laborious and without recognition.'
Er ist ein undankbarer Mensch, der nie zufrieden ist.
He is an ungrateful person who is never satisfied.
If you want to express what someone is ungrateful for, use the preposition 'für' (for) followed by the accusative.
Sie war undankbar für all die Hilfe, die sie bekommen hatte.
She was ungrateful for all the help she had received.
In the meaning 'without recognition,' the word is almost always used in the combination 'eine undankbare Aufgabe' (a thankless task) or 'eine undankbare Arbeit' (thankless work).
Die Organisation des Festes war eine undankbare Aufgabe, weil sich am Ende alle nur beschwert haben.
Organizing the party was a thankless task because in the end everyone only complained.
grateful
'dankbar' and 'undankbar' are direct opposites. For people, 'dankbar' means that someone appreciates help or kindness; 'undankbar' means that someone does not show this appreciation. With tasks, there is also a contrast: a 'dankbare' Aufgabe is a rewarding task that quickly produces a good result, while an 'undankbare' Aufgabe is difficult, unpleasant, or receives little recognition. So the context shows whether it is about a feeling or about a task.

Die Pflege der alten Geräte ist eine undankbare Aufgabe, weil kaum jemand die Arbeit sieht.
Maintaining the old equipment is a thankless task because hardly anyone sees the work.
Der Kunde war dankbar, weil die Köchin ihm trotz der späten Stunde noch half.
The customer was grateful because the cook still helped him despite the late hour.