This is the 878th most frequent Turkish word.
etkisiz
Ineffective; powerless; neutralized.
In this sentence, 'etkisiz' means 'ineffective', indicating that the medicine lacks the desired effect.
Bu ilacın etkisiz olduğunu gördük.
We observed that this medicine is ineffective.
Here, 'etkisiz' is used to predict that a certain method will not work as intended.
Bu yöntemin etkisiz olacağını sanıyorum.
I believe that this method will be ineffective.
In this context, 'etkisiz' is describing speeches that fail to make an impact or leave a mark.