This is the 83rd most frequent Hindi word.
यह
"This."
In this sentence, 'यह' is used as a demonstrative pronoun, referring to the object being talked about.
यह एक किताब है।
This is a book.
Here, 'यह' acts as a demonstrative adjective modifying the noun 'पुस्तक', describing which book is interesting.
यह पुस्तक बहुत रोचक है।
This book is very interesting.
In this sentence, 'यह' is part of the term 'यहाँ', meaning 'here', giving a sense of the location being described.