Topic marker wa

The topic phrase generally appears at the beginning of a sentence. Compare the sentences with and without a topic.

ジョンがこの本を書きました。 Jon ga kono hon o kakimashita. (no topic) John wrote this book.

この本はジョンが書きました。 Kono hon wa Jon ga kakimashita. (kono hon wa is the topic.) Speaking of this book, John wrote it.