1. Indefinite Article
A or An: Originate as same as "one", is mainly used before countable singular noun.
1.1 Means one, as a number :
- Rome wasn't built a day.
- She is a friend of mine.
- I take that bus 2 times a day.
- The ship goes by 30 km an hour.
- A car is waiting at the door.
1.2 Means someone, not specified to certain thing or person :
- He was born in a small city.
- They are waiting for a visitor.
- An interesting story always makes kids laugh.
- She is a Canadian writer.
1.3 Means one type or class of something :
- A child needs love.
- An owl can see in the dark.
- An honest man usually is a fair man.
2. Definite Article
The: Originate as same as "this" or "that", weaker than "this" or "that" but can be used on both singular and plural objects; it can be used with adjective too.
2.1 Means specific thing or things before singular or plural Individual noun :
- Where are the other girls?
- Put the phone on my desk.
- Show the quests our meeting room.
- Did you go to the opening ceremony?
Other nouns, not individual nouns, should be led by definite article too, only if they represents specific thing. For example,
- Pass me the salt. (Mass Nouns)
- Take the medicine now. (Mass Nouns)
- I like the children's performance. (Abstract Nouns)
When we mention something second time in context, use definite article to specify it. For example,
- I buy a computer and a printer, but I dislike the printer.
- I enter a house in the street and see the rooms are very clean.
2.2 Means a specific type of something before singular noun :
- The whale is in danger of extincting.
- The 18 century is the golden age of the novel.
- The plane has made the earth smaller.
- The computer is changing our life.
2.3 Means the whole of an ethnic, class, or family before noun :
- The Thompsons arrived at 8 o'clock.
- The Japanese people like sushi.
- They represent the interests of the middle class.
2.4 Used before noun to express unique object :
- Do you know how big the universe is?
- The sun lights the earth.
- The Mike Way is bright in the sky.
- The moon is in the middle of the air.
- They arrived the North Pole.
- His shuttle is leaving the outer space.
2.5 Used before adjective to express a type of people :
- He shouldn't be among the unemployed.
- These seats are for disabled.
- Either the rich or the poor have same right to vote.
2.6 Used before adjective to form a noun phrase :
- Our goal is to discover the good, the beautiful, and the true.
- She admires the mystical.
- I like to venture the unknown.