Questions & Answers about Dat raam is groot.
Why is it dat raam and not die raam?
In Dutch, the word for 'that' changes depending on whether the noun is a de word or a het word. Because raam is a het word (het raam), we use dat to say 'that'. If it were a de word, like de deur (the door), you would say die deur.
Could dat also mean 'this'?
No, dat always points to something farther away ('that'). If you wanted to say 'this window' (pointing to something close by), you would use the word dit because raam is a het word (dit raam).
Why doesn't groot have an -e at the end here?
When an adjective comes directly after a verb like is, it never gets an extra -e ending. You only need to worry about adding an -e when the adjective comes right before the noun, as in het grote raam (the big window).