Is there any particular reason for using the or a? Is there any specific rule applied?

When the is omitted, what should I notice instead of the generic noun?

For example, what is the difference in the following?

  1. I am seeing a train.
  2. I am seeing the train.
  • There are plenty of explanations readily available. Google search for "definite indefinite articles english". For example Purdue OWL: How to Use Articles (a/an/the).
    – user485
    Apr 12, 2013 at 4:48
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    You might also like to try this: halfbakedsoftware.com/quandary/version_2/examples/articles.htm Apr 12, 2013 at 6:46
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    @user3169. The first sentence of the OWL article doesn't inspire confidence. Apr 12, 2013 at 7:10
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    A lot of English learners love to use continuous tenses like "I am seeing". Continuous tenses do have their purpose, but this is not one of them. Instead, say I see a train or I see the train. (The only time a native speaker is likely to string together the words "I", "am", and "seeing" is if the next word is "things".)
    – Martha
    Apr 12, 2013 at 14:16
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    @Martha: Also idiomatically in the context of "seeing someone" meaning in a relationship with that person: e.g. I want a divorce - this marriage isn't working. It's not you, it's me. I am seeing someone else.
    – Matt
    Apr 12, 2013 at 14:27

1 Answer 1


A lot can be said about this, that is why it is a good idea to just google it. But to give you a general idea:

"a" is used before singular countable nouns, not preceded by "the" or a possessive pronoun.

"the" is used when the listener knows what the speaker is referring to, when the noun is defined. That is why it is called a "definite article".

A noun is defined when:

  • there is only one (the sun, the moon). I would include superlatives here because only one can be the most of something (the best singer, the richest person)
  • there is only one in that place, for example you will say: "Open the window!" when there is only one window in the room.
  • it has already been mentioned before (e.g. I saw a man. The man was wearing a blue shirt.)
  • there is information which defines it (e.g. "The woman is here." makes you ask "Which woman?" but if you say "The woman who called you earlier is here.", it is clear.

In your example, "I am seeing a train" is a general statement. There is a train and you see it. "I am seeing the train" means that you see a train you were expecting, or one that you had been talking about before. For example, if you are waiting to meet someone at the station and their train is arriving, you see "the train", the one that your friend is in.

  • This is a pretty good start, but there are plenty of exceptions, too. I might say, "Open the window!" in a location with two windows, particularly if it's obvious which one I'm referring to (such as when I'm driving a car, and talking to a passenger). But, as you said, this gives a good general idea.
    – J.R.
    Apr 12, 2013 at 14:52
  • Absolutely! What J.R. is saying confirms the rule that we use "the" when we know which one we are talking about.
    – fluffy
    Apr 12, 2013 at 15:03
  • You can also use "the" before a plural, if your defined noun is a set of objects.... "Close the windows! Bar the doors!"
    – Hellion
    Apr 12, 2013 at 15:43
  • @J.R. In what conditions would you 'omit' the word "the" before noun, instead of generic noun? Apr 12, 2013 at 16:44
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    @Des, we omit "the" (use no article) when we generalize, as you said, as well as with some proper nouns: most streets, villages, towns, cities, countries, lakes, mountains (Oxford Street, Mount Fuji). But, and this is where it gets tricky, we DO use a definite article with names of rivers, oceans, seas, names of places which are plural (the Netherlands, the Himalayas), the names of countries which have the words states, kingdom or republic in them (we say China, but the Republic of China).
    – fluffy
    Apr 13, 2013 at 6:26

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