persistent
US /pɚˈsɪs.tənt/
UK /pɚˈsɪs.tənt/
1.
continuing firmly or obstinately in a course of action in spite of difficulty or opposition
:
•
She was persistent in her efforts to learn English.
•
His persistent questioning eventually led to the truth.
2.
(of an unwanted phenomenon) continuing to exist or occur over a prolonged period
:
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The persistent cough kept him awake all night.
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We need to find a solution for this persistent problem.