This is the 17th most frequent Hindi word.
कई
Several; many.
Here, 'कई' specifies an indefinite quantity, meaning 'many' students.
कई छात्र पुस्तकालय में पढ़ रहे हैं।
Many students are studying in the library.
In this sentence, 'कई' again signifies 'many,' addressing the plural nature of 'people' who like the book.
कई लोग इस पुस्तक को पढ़ना पसंद करते हैं।
Many people like to read this book.
Here, 'कई' indicates 'several' occurrences, showing the repeated nature of the action.