Understand how to form a prepositional phrase.

Prepositions generally introduce prepositional phrases. Prepositional phrases look like this:

preposition + optional modifiers

+ oun, pronoun, or gerund

Here are some examples:

At school

At = preposition; school = noun.

According to us 

According to = preposition; us = pronoun. 

By chewing

By = preposition; chewing = gerund. 

Under the stove

Under = preposition; the = modifier; stove = noun. 

In the crumb-filled, rumpled sheets

In = preposition; the, crumb-filled, rumpled = modifiers; sheets = noun. 

Indefinite articles - a and an

A and an are the indefinite articles. They refer to something not specifically known to the person you are communicating with.
A and an are used before nouns that introduce something or someone you have not mentioned before:-

For example:

"I saw an elephant this morning." "I ate a banana for lunch."

A and an are also used when talking about your profession:-

For example:

"I am an English teacher." "I am a builder."

Note!

You use a when the noun you are referring to begins with a consonant (b, c, d, f, g, h, j, k, l, m, n, p, q, r, s, t, v, w, x, y or z), for example, "a city", "a factory", and "a hotel". You use an when the noun you are referring to begins with a vowel (a, e, i, o, u) Pronunciation changes this rule. It's the sound that matters, not the spelling. If the next word begins with a consonant sound when we say it, for example, "university" then we use a. If the next word begins with a vowel sound when we say it, for example "hour" then we use an. We say "university" with a "y" sound at the beginning as though it were spelt "youniversity". So, "a university" IS correct. We say "hour" with a silent h as though it were spelt "our". So, "an hour" IS correct.

สรุป การใช้ Articles

ใช้ a, an นำหน้านามที่เป็นสำนวนเกี่ยวกับการเจ็บไข้ได้ป่วย

โครงสร้างคือ have + a+ อาการเจ็บป่วย 
(cold, fever , headache , ulcer , bruise , 
sprain , flu , stitch , cramp) ตัวอย่างเช่น 
have a headache ( ปวดหัว ) 
have a pain in the chest ( เจ็บหน้าอก ) 
have a stomachache ( ปวดท้อง ) 
have a cold ( เป็นหวัด ) 

have a toothache ( ไม่มี a ก็ได้ ) ( ปวดฟัน )
have a fever ( เป็นไข้ )

ใช้ a, an นำหน้านาม 
มีข้อยกเว้นถ้าเป็นชื่อโรค ไม่ใช้ a, an เช่น
rheumatism( โรคปวดข้อ ) ,
diabetes ( เบาหวาน ),
influenza (ไข้หวัดใหญ่ ) ,
cancer ( มะเร็ง )
cholera (อหิวาตกโรค) ,
smallpox (ฝีดาษ) , 

ใช้ the นำหน้านาม
การใช้ the กับชื่อเฉพาะ ( proper noun)
*ชื่อเฉพาะของลักษณะทางภูมิศาสตร์ได้แก่ แม่น้ำ มหาสมุทร ทะเล อ่าว คลอง ช่องแคบ คาบสมุทร ทะเลทราย หมู่เกาะ เทือกเขา กลุ่มทะเลสาบ แหลม ป่า ตัวอย่างเช่น
แม่น้ำ : the Chow Praya (River ) , the Nile, the Thames, the Mississippi
มหาสมุทร: the Pacific ( Ocean ), the Atlantic (

 Ocean ), the Indian Ocean,
ทะเล : the Mediterranean (Sea) , the Dead Sea, the China Sea, the Red Sea
อ่าว : the Gulf of Thailand , the Gulf of Mexico, the Persian Gulf
คลอง : The Suez ( Canal ), the Panama ( Canal )
ช่องแคบ: the English Channel, the Straight of Malacca, the Straight of Gibraltar
คาบสมุทร : the Indo-China Peninsula, the Scandinavian Peninsula, the Iberian Peninsula
ทะเลทราย: the Sahara ( Desert ) , the Gobi (Desert)
แหลม : the Cape of Good Hope ( แต่ถ้าไม่มี of ไม่ต้องใช้ the เช่น Cape Canaveral )
ป่า: the Black Forest ,the Redwood Forest, the Amazon Forest

ไม่ใช้ the นำหน้านาม
การไม่ใช้ the กับ......
1. ชื่อมื้ออาหาร breakfast , lunch
2. ชื่อกีฬา football , volleyball
3. ชื่อจังหวัด, เมือง, ประเทศ
4. ชื่อวิชา English, French, History

Credit: มาสเตอร์ ปรีชา ตันวัฒนานันท์

What is an article? Basically, an article is an adjective. Like adjectives, articles modify nouns.

English has two articles: the and a/an. The is used to refer to specific or particular nouns;a/an is used to modify non-specific or non-particular nouns. We call the the definite article and a/an the indefinite article.

the = definite article

a/an = indefinite article

For example, if I say, "Let's read the book," I mean a specific book. If I say, "Let's read abook," I mean any book rather than a specific book.

Here's another way to explain it: The is used to refer to a specific or particular member of a group. For example, "I just saw the most popular movie of the year." There are many movies, but only one particular movie is the most popular. Therefore, we use the.

"A/an" is used to refer to a non-specific or non-particular member of the group. For example, "I would like to go see a movie." Here, we're not talking about a specific movie. We're talking about any movie. There are many movies, and I want to see any movie. I don't have a specific one in mind.

Let's look at each kind of article a little more closely.

Indefinite Articles: a and an

"A" and "an" signal that the noun modified is indefinite, referring to any member of a group. For example:

• "My daughter really wants a dog for Christmas." This refers to any dog. We don't know which dog because we haven't found the dog yet.
• "Somebody call a policeman!" This refers to any policeman. We don't need a specific policeman; we need any policeman who is available.
• "When I was at the zoo, I saw an elephant!" Here, we're talking about a single, non-specific thing, in this case an elephant. There are probably several elephants at the zoo, but there's only one we're talking about here.

Remember, using a or an depends on the sound that begins the next word. So...

• a + singular noun beginning with a consonant: a boy; a car; a bike; a zoo; a dog
• an + singular noun beginning with a vowel: an elephant; an egg; an apple; an idiot;an orphan
• a + singular noun beginning with a consonant sound: a user (sounds like 'yoo-zer,' i.e. begins with a consonant 'y' sound, so 'a' is used); a university; a unicycle
• an + nouns starting with silent "h": an hour
• a + nouns starting with a pronounced "h": a horse
  • In some cases where "h" is pronounced, such as "historical," you can use an. However, a is more commonly used and preferred.
    A historical event is worth recording.

Remember that these rules also apply when you use acronyms:

Introductory Composition at Purdue (ICaP) handles first-year writing at the University. Therefore, an ICaP memo generally discusses issues concerning English 106 instructors.

Another case where this rule applies is when acronyms start with consonant letters but have vowel sounds:

An MSDS (material safety data sheet) was used to record the data. An SPCC plan (Spill Prevention Control and Countermeasures plan) will help us prepare for the worst.

If the noun is modified by an adjective, the choice between a and an depends on the initial sound of the adjective that immediately follows the article:

• a broken egg
• an unusual problem
• a European country (sounds like 'yer-o-pi-an,' i.e. begins with consonant 'y' sound)

Remember, too, that in English, the indefinite articles are used to indicate membership in a group:

• I am a teacher. (I am a member of a large group known as teachers.)
• Brian is an Irishman. (Brian is a member of the people known as Irish.)
• Seiko is a practicing Buddhist. (Seiko is a member of the group of people known as Buddhists.)

Definite Article: the

The definite article is used before singular and plural nouns when the noun is specific or particular. The signals that the noun is definite, that it refers to a particular member of a group. For example:

"The dog that bit me ran away." Here, we're talking about a specific dog, the dog that bit me.

"I was happy to see the policeman who saved my cat!" Here, we're talking about aparticular policeman. Even if we don't know the policeman's name, it's still a particular policeman because it is the one who saved the cat.

"I saw the elephant at the zoo." Here, we're talking about a specific noun. Probably there is only one elephant at the zoo.

Count and Noncount Nouns

The can be used with noncount nouns, or the article can be omitted entirely.

• "I love to sail over the water" (some specific body of water) or "I love to sail over water" (any water).
• "He spilled the milk all over the floor" (some specific milk, perhaps the milk you bought earlier that day) or "He spilled milk all over the floor" (any milk).

"A/an" can be used only with count nouns.

• "I need a bottle of water."
• "I need a new glass of milk."

Most of the time, you can't say, "She wants a water," unless you're implying, say, a bottle of water.

Geographical use of the

There are some specific rules for using the with geographical nouns.

Do not use the before:

• names of most countries/territories: Italy, Mexico, Bolivia; however, the Netherlands,the Dominican Republic, the Philippines, the United States
• names of cities, towns, or states: Seoul, Manitoba, Miami
• names of streets: Washington Blvd., Main St.
• names of lakes and bays: Lake Titicaca, Lake Erie except with a group of lakes likethe Great Lakes
• names of mountains: Mount Everest, Mount Fuji except with ranges of mountains likethe Andes or the Rockies or unusual names like the Matterhorn
• names of continents (Asia, Europe)
• names of islands (Easter Island, Maui, Key West) except with island chains like theAleutians, the Hebrides, or the Canary Islands

Do use the before:

• names of rivers, oceans and seas: the Nile, the Pacific
• points on the globe: the Equator, the North Pole
• geographical areas: the Middle East, the West
• deserts, forests, gulfs, and peninsulas: the Sahara, the Persian Gulf, the Black Forest, the Iberian Peninsula

Omission of Articles

Some common types of nouns that don't take an article are:

• Names of languages and nationalities: Chinese, English, Spanish, Russian (unless you are referring to the population of the nation: "The Spanish are known for their warm hospitality.")
  
• Names of sports: volleyball, hockey, baseball
• Names of academic subjects: mathematics, biology, history, computer science