This is the 17th most frequent Malay word.
ia
"It" or "he/she" (third-person pronoun).
In this sentence, 'ia' is used as a pronoun to refer to the subject, which is 'an interesting book'.
Ia adalah sebuah buku yang menarik.
It is an interesting book.
Here, 'ia' serves as an object pronoun, referring to 'it' which was told to the teacher.
Saya memberitahu ia kepada guru.
I told it to the teacher.
In this usage, 'ia' functions as a subject pronoun referring to a person, either 'he' or 'she'.