This is the 58th most frequent Malay word.
sebuah
A classifier for a singular object.
The word 'sebuah' is used here as a numeral classifier for the noun 'buku' (book) to specify a singular item.
Saya membeli sebuah buku.
I bought a book.
In this sentence, 'sebuah' classifies the noun 'rumah' (house), emphasizing its singularity.
Kami akan membina sebuah rumah di kawasan itu.
We will build a house in that area.
Here, 'sebuah' serves as a numeral classifier for 'jam tangan' (watch), marking it as a single entity.