A – one in particular

Refer to a specific item (first mention)

Hale-Bopp comet


A – Unspecific (any one) vs. A – Specific (particular one)


When referring to an item the first time, the article a is used before a noun. The article is changed to the on second mention.

A comet was seen in the western sky last night. (first mention)

The comet was believed to be Hale-Bopp. (second mention)

The comet has a spectacular, bright tail. (second mention)



When speaking in general, mentioning characterics of a particular item, the article a is used before a noun. "This is true for any like it."

A comet appears to have a tail as it streaks through the sky.

A comet also has a dense head.

If you look up in the sky, you might see a comet.


Astronomy and Space Resource







Practice 1

A Particular One or Any One?

a black hole



Any one or a particular one?

  1. Select your response.
  2. Compare your response to the feedback by clicking the "check" button.


A black hole is an object, typically a collapsed star whose gravity is so strong that its escape velocity exceeds the speed of light. Since nothing is known to exceed the speed of light, nothing can escape from a black hole.

A black hole

A planet was later discovered farther out in the solar system. The planet, Jupiter, named after the Roman god, was the largest of all.

A planet








Practice 2

Any One or a Particular One ?

a comet



A particular one (specific) or any one (unspecific)?

  1. Select the response from the list that best completes the sentence. 
  2. Compare your response to the feedback by clicking the "check" button.


People did not always know what a comet was. In ancient times, people thought comets were "power rays" of super- natural beings.


They thought a comet contained fire because they are so bright in the sky.


Some people in ancient times thought that a comet was a curse. To save himself from "the curse of the comet", Emperor Nero of Rome has all possible successors to the throne executed.


In 1910, people panicked when a comet passed through Earth's path around the Sun.


In Chicago, people sealed their windows to protect themselves from a comet that they believed had a poisonous tail. Others committed suicide. Special "comet protecting umbrellas", gas masks, and "anti-comet pills" were sold.


Not everyone saw a comet as bad luck. Some thought a comet brought good luck.


They also believed that a comet carried angels through the heavens.



Amazing Space: Online Explorations (NASA) http://amazing-space.stsci.edu 
"Comets Facts, Myths and Legends" Amazing Space, 2011, http://amazing-space.stsci.edu/resources/explorations/cometmyth/home.html