ineffective
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ineffective
Without achieving the intended effect, or any noticeable effect at all; ineffective or futile.
Alle seine Versuche, das Feuer zu löschen, blieben wirkungslos.
All his attempts to put out the fire remained ineffective.
The adjective has a simple structure: it consists of the noun 'die Wirkung' (effect) and the suffix '-los' (-less), which means 'without'. So 'wirkungslos' (ineffective) literally means 'without effect'.
Leider war das neue Medikament bei ihm völlig wirkungslos.
Unfortunately, the new medication was completely ineffective for him.
'Wirkungslos' (ineffective) is very often used with the verb 'bleiben' (to remain). The construction 'wirkungslos bleiben' (to remain ineffective) emphasizes that an expected effect did not occur.
Trotz der vielen Proteste blieben die Appelle der Bürger wirkungslos.
Despite the many protests, the citizens' appeals remained ineffective.
The word often describes things from which one had hoped for an effect. Typical combinations are 'wirkungslose Maßnahmen' (ineffective measures), 'wirkungslose Medikamente' (ineffective medications), or 'wirkungslose Versuche' (ineffective attempts).
Sein Versuch, sie zu überzeugen, war leider wirkungslos.
His attempt to convince her was unfortunately ineffective.
unsuccessful
Erfolglos means that the desired goal was not achieved, even though some effect may have occurred. Wirkungslos, by contrast, means that no intended or noticeable effect can be observed. In the case of a treatment, the key question is therefore whether all effects were absent or only the cure was not achieved.
Die Behandlung war wirkungslos, denn weder die Schmerzen noch der Zustand des Patienten veränderten sich.
The treatment was ineffective because neither the pain nor the patient's condition changed.
Die Behandlung blieb erfolglos, obwohl sie die Schmerzen linderte, denn der Patient wurde nicht gesund.
The treatment was unsuccessful even though it relieved the pain, because the patient did not recover.
