Learn English Basic Grammar With Simple Examples

If I Say --
I have a black and white dog.
I mean a dog that is partly black and partly white.
But if I say--

• I have a black and a white dog.
• I mean two dogs, one black and the other white. 

Hence when two or more adjectives qualify the same noun, the Article is used before the first adjective only; but when they qualify different nouns, expressed or understood, the Article is normally used before each adjective.
Compare--

1. The Secretary and Treasurer is absent. 
2. The secretary and the Treasurer are absent. 

The first sentence clearly indicates that the posts of Secretary and Treasurer are held by one person.
The repetition of an article in the second sentence indicates that the two posts are held by two different persons.
Hence we see that when two or more connected nouns refer to the same person or thing, the Article is ordinarily used before the first only; but when two or more connected nouns refer to different persons or things, the article is used before each.
Also examine the following sentences:

• John was a great orator and statesman. 
• There are on the committee among others a great economist and a great lawyer.  

We may either say--

• The third and the fourth chapter.
• (or) The third and the fourth chapters.

In expressing a comparison, if two nouns refer to the same person or thing, the Article is used before the first noun only;as;

• He is a better mechanic than clerk.
• He is a better poet than novelist. 
• He is a better thinker than debater.
• He would make a better engineer than lawyer. 

But if they refer to different persons or things, the article must be used with each noun;as,

• He is a better mechanic than clerk.
• He would make a better statesman than a philosopher (would make).