He is coming from the east.
We use an before hour.
An is an article here.
Hour gives vowel sound.
Kilo gives consonant sound.
He boasts of having a good knowledge of mathematics but everybody knows how far he is good at mathematics.
Here the poor means all the poor living in the world.
Here the sick means all the sick living in the world.
This is not an easy question.
یہ ایک آسان سوال نہیں ہے۔
Articles "A" and "AN" are used with some expressions.
For example:
Make a noise, give a warning, have a pain, have a great education etc.
Here a means only one policeman.
Policeman gives consonant sound.
A is an article
A is used before consonant sound (good)
He is a good boy.
وہ ایک اچھا لڑکا ہے۔
No article required before uncountable noun.
Poetry is an uncountable noun.