Steadfastly(adverb)
(In a resolutely or dutifully firm and unwavering manner.)
Hindi meaning:दृढ़तापूर्वक
Synonyms: Resolutely, Firmly, Securely, Solidly, Staunchly
Antonyms: Loosely, waveringly
Example: The soldiers stood steadfast against the approaching enemy army.
Trick to remember: Aesi fast skating Steadfastly hone pe hi hoti hai 
