There are several words in Indonesian that don’t have any equivalent in English and “yang” is one of  those.  “Yang” can be translated as ‘the’, ‘the one’, ‘which’, ‘who’, and ‘that’ .

For example: Yang + adjective

When the qualifier of a noun is an adjective such as ‘white’ as ‘white book’ as ‘clever’ as in ‘clever boy’, the Indonesian equivalent often has yang inserted in between the noun and adjective. Thus buku yang putih, and anak yang pandai are literally translated as ‘the book which is white’ and ‘the boy who is clever’. This way the speaker points out the object more clearly. This is especially necessary when the mood of the speaker is comparative:

kalkulator saya yang kecil – my small calculaor (lit.: my calculator which is small not that big one)

sepatu saya yang hitam – my black shoes (lit.: my shoes which are black not white)

komputer saya yang baru – my new computer (lit.: my computer which is new; the one I just bought)

1. A noun plus adjective phrase forms a close unit, expressing a single idea without any emphasis on the adjective. An adjective immediately follows the phrase head:

Examples:

rumah besar	a big house
gedung tinggi	a tall building
komputer baru	a new computer

Adjectives are frequently preceded by “yang” (It is optional).

Examples:

rumah  yang besar	a big house
gedung yang tinggi	a tall building
komputer yang baru	a new computer

In sentences, the examples are:

Dia tinggal di rumah besar.	He lives in a big house.
Gedung tinggi itu terletak di New York.	That tall building is located in New York.

“Yang” separates the adjective from the noun and gives emphasis to it.  This happens, for instance, when a contrast is made:

Mereka tinggal di rumah yang besar, tidak di rumah yang kecil.

They live in a big house, not a small house.

However, some noun-plus-adjective phrases are either compounds, with idiomatic meaning, or genuine phrases depending on context. The combination can only be separated by “yang” if it is not a compound.

rumah sakit	hospital
imigran gelap	illegal immigrant
orangtua – parents		orang yang tua – an old people
kamar kecil – toilet		kamar yang kecil – a small room
meja hijau – law court		meja yang hijau – a green table
kambing hitam – scapegoat		kambing yang hitam – black (colored) goat

If more than one adjective occurs, the first may form a close unit with the noun while the second is preceded by “yang”; so “yang” is used to join an adjective to the noun it describes (optional, but often felt to be better style, especially when there are two adjectives) :

Examples:

gadis kuno yang malu-malu	a shy old-fashioned girl
tubuh tua yang ringkih	a frail old body
rumah baru yang indah	a beautiful new house

Coordinated adjectives must be preceded by yang:

Examples:

anak yang rajin dan pandai	a hard-working and clever child
toko yang baru dan lengkap	a new and complete shop
bank yang besar dan modern	a big and modern bank

A sequence of more than two adjectives usually requires dan”and” only before the final adjective:

Examples:

wanita yang cantik, periang dan cerdas	a woman who is beautiful, cheerful and intelligent
anak yang gembira, sehat dan kuat	a child who is happy, healthy and strong
ayah yang sehat, gagah dan berani	a father who is healthy, dashing and daring

As “yang” actually introduces a relative clause, predicate elements such as negative and temporal markers can precede the adjective:

Examples:

Pakaian yang tidak mahal ada di pasar – pasar tradisional.	Clothes which aren’t expensive are in traditional markets.
Orang yang sudah capai akan tidur.	People who are already tired will go to sleep.

With other adjective phrases “yang” is obligatory: 

Examples: 

jas yang terlalu besar	a jacket which is too big
orang yang lebih kaya	richer people