sebuah = sebuah telur, sebuah buku, sebuah cerita, sebuah lagu. an egg, a book, a story/saga, a song. seorang = Seorang anak, seorang ibu, seorang bapak, seorang nenek (humans only) a boy/ a girl, a mother, a father, a grandmother sepotong = sepotong kue, sepotong kayu, sepotong kain. a piece of cake/ a slice of bread sebatang = sebatang pohon, sebatang kayu, sebatang pensil, sebatang penggaris. sehelai = sehelai rambut, sehelai kain sepasang = sepasang sepatu, sepasang sandal ( in pairs of ...) sebutir = sebutir telur ( an egg), sebutir pil, sebutir tablet. sepiring = sepiring nasi, sepiring makanan / semangkuk sayuran, semangkuk buah.( talking about foods) seekor = seekor kambing, seekor ayam ( talking about animals).

For more explanation perhaps you can find here >>> http://bahasakita.com/about/grammar/prefix/se/

These are classifiers for nouns, and you choose the classifier based on the shape/form of the actual noun. For example, "seorang" = se(satu, 1) + orang (person), so you only use "seorang" for humans. Seorang wanita - "one(person) woman". Sebuah literally means "one-fruit", but it covers nouns with solid dimensions, eg. sebuah rumah - "one house" Remove "se-" from the classifier and you'll get an idea of which classifier may go with which noun.