How to use 'adalah' correctly

As promised, here is the post on the correct usage of 'adalah'.

'adalah' (is) is often wrong used when 'ialah' should be used. Now, let us see how to use 'adalah' correctly.

'adalah' is used in front of 'frasa adjektif' (adjectival phrase) and 'frasa sendi nama' (prepositional phrase). The following examples will make this rule clear to readers.

1 Kereta yang dibelinya itu adalah terlalu mahal dan saya tidak mampu memilikinya.
[The car that he bought is too expensive and I can't afford to own it.]
In the above sentence, 'terlalu mahal' is an 'frasa adjektif' or adjectival phrase.

2 Surat yang saya baca ini adalah daripada sahabat penaku.
[The letter I am reading is from my pen-pal]
'daripada sahabat penaku' is 'frasa sendi nama' or prepositional phrase.

3 Hadiah ini adalah untuk adikmu.
[This present is for your younger brother.]
The prepositional phrase here is 'untuk adikmu'.
Note that 'untuk' here is considered as a preposition because it is used in front of a noun (adik).
It can be a conjunction if it is used in front of a vcrb. For example, the 'untuk' in the sentence below is not a preposition but a conjunction:
Dia pergi ke kedai itu untuk membeli ubat.
[He went to the shop to buy medicine.]

4 Peraturannya adalah sepert yang berikut.
[The rules are as follows.]
In the above sentence, 'seperti' is a preposition.

I hope the above explanation is clear to readers as to how 'adalah' should be used.