Explanation

• I really hate traveling by air.
• مجھے واقعی ہوائی سفر سے نفرت ہے۔
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• Really  is best to keep the meaning of the original sentence
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• Really is an adverb, and it modifies other adverbs, verbs, or adjectives. It has a meaning of "very." 
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• start a sentence with really
• Really can be used in the following ways: as an adverb (with a verb):
• Do you really love her? (before an adjective or adverb)