Introducing one object into the conversation
Use a with one countable object, such as a bag, ticket or chair. The noun must be singular. The article marks the noun phrase as indefinite; it does not need a separate dictionary meaning in every sentence.
If you need a pen without identifying a particular pen for the listener, say a pen: one member of that kind. You may know which pen you mean yourself, but you are not presenting it as something the listener can already identify.
I need a bag.
I need a bag.
The speaker needs one bag, without identifying a particular bag that both people already know about.
There is a chair by the window.
There is a chair by the window.
The chair is newly introduced into the description. The word chair begins with a consonant sound.
A before a consonant sound
Say the next word aloud. If its first sound is a consonant, choose a: bag begins with /b/ and ticket with /t/. Symbols between slashes represent sounds, not the names of letters.
A and an are two forms of the same indefinite article. Use an before a vowel sound. This does not mean every singular noun needs a: first decide whether an indefinite article is appropriate.
a + word beginning with a consonant sound + the rest of the noun phrase
- NP / noun phrase —
- A noun phrase: a noun with its dependent words, such as the new student; the pattern treats it as one group of words.
- noun —
- A word naming a person, thing or idea: student, book, happiness.
Can I buy a ticket here?
Can I buy a ticket here?
The word immediately after the article is ticket, which begins with /t/.
We need a table and an extra chair.
We need a table and an extra chair.
Table begins with a consonant sound, while extra begins with a vowel sound. Check each noun phrase separately.
A vowel letter does not always represent a vowel sound
University, uniform, useful and European begin with the consonant sound /j/, as in yes. In /juː/, the first sound is /j/, even though a vowel follows it.
One begins with /w/, as in we, not with a vowel sound suggested by the letter o. This gives a one-way ticket. These words follow the sound rule; they only contradict a rule based on letters. Check the pronunciation of an unfamiliar word in a dictionary.
This is a university building.
This is a university building.
Use a because university begins with /j/.
We want to visit a European city.
We want to visit a European city.
European begins with /j/. The sentence does not identify a particular city already chosen by the speakers.
I need a one-way ticket.
I need a one-way ticket.
One-way begins with /w/, although its first written letter is o.
Listen to the word immediately after the article
If an adjective comes before the noun, its first sound determines the article: a small office, but an office. Place the article before the whole noun phrase, not between the adjective and noun.
The shorthand “a + noun” applies when no adjective intervenes. The fuller pattern is article + optional description + noun. Remember that letters and sounds differ: c represents /k/ in cat and /s/ in city, but both sounds are consonants.
a + adjective beginning with a consonant sound + singular countable noun
- noun —
- A word naming a person, thing or idea: student, book, happiness.
- adjective —
- A word describing what someone or something is like: happy, tired, interesting.
I work in a small office.
I work in a small office.
The next word is small, which begins with /s/. The first sound of the more distant word office does not determine the article.
This is a useful app.
This is a useful app.
Useful begins with /j/, so use a, even though app begins with a vowel sound.
I have an old bag.
I have an old bag.
Old is closer to the article than bag and begins with a vowel sound, so a would be incorrect here.
The limits of this rule
Do not use a with plural nouns: a box, but two boxes. An uncountable substance does not become an individual object simply by adding an article: say water or a bottle of water. Plural and uncountable nouns need separate study.
The answers a different question: can the listener identify the item? I need the key can be correct in a suitable context; this is not a pronunciation error. In an exercise, the context or an instruction to choose between a and an establishes the indefinite meaning.
Professions, geographical names, fixed expressions, abbreviations and words with variant pronunciations are outside the scope of this exercise. Words such as hour and umbrella illustrate the vowel-sound boundary, rather than providing a complete lesson on an.
I have a box. I also have two bags.
I have a box. I also have two bags.
Use a with one box. The plural noun bags does not take a.
Can I have a bottle of water?
Can I have a bottle of water?
The countable unit is a bottle, not the water. The article belongs to bottle, which begins with /b/.
Using a in your own reply
Ask yourself: am I referring to one item, can the listener already identify it, and what sound follows the article? Then build the phrase: a red bag, a useful map.
An open exercise provides a model and a way to check your answer, not necessarily the only possible reply. Natural word choices and polite forms are acceptable. Check meaning, article use and the task requirements separately. Written answers do not demonstrate pronunciation. You may invent personal details.
Could I borrow a pen, please?
Could I borrow a pen, please?
The speaker asks for any suitable pen, without identifying a particular pen already known to both people. Pen begins with /p/.
A small bag, please.
A small bag, please.
This is a natural short reply to a shop assistant. If the task requires a full sentence, it does not meet that requirement, but its article is correct.
Common mistakes
Incorrect:I need an key.
Correct:I need a key.
Key begins with the consonant sound /k/, so change only the article to a.
Incorrect:This is an university building.
Correct:This is a university building.
University begins with /j/. The vowel letter u does not justify an.
Incorrect:I need an useful app.
Correct:I need a useful app.
The next word is useful, beginning with /j/, not the more distant noun app.
Incorrect:We have small a office.
Correct:We have a small office.
The article belongs before small, which begins with /s/: a small office.
Incorrect:I have a bags.
Correct:I have bags.
Bags is plural. Its initial consonant sound does not make a possible.
Incorrect:I have a old phone.
Correct:I have an old phone.
Old begins with a vowel sound and needs an, even though phone begins with a consonant sound.