This is the 705th most frequent Finnish word.
tätä
The Finnish word "tätä" means "this" in the partitive case.
Here, 'tätä' is used in its form 'tästä,' a case form indicating 'about this.' The word refers to the specific item 'book' that is being liked.
Pidän tästä kirjasta paljon.
I like this book a lot.
'Tätä' refers to 'this,' as part of its nominative singular form, modifying 'problem' to specify it.
Tätä ongelmaa ei ole helppo ratkaista.
This problem is not easy to solve.
In this sentence, 'tätä' (in the form 'tästä') is used to indicate something specific that is being liked, with the verb 'pitää'.