Do I have to use a/an articles before singular nouns, always or can I eliminate them? Is this true? I saw dog yesterday.
Singular countable nouns always need a determiner; plural, proper and uncountable nouns do not need a determiner. (Source: http://www.quickanddirtytips.com/education/grammar/when-to-use-articles-before-nouns)
Examples of determiners are the, those, a, an, their, etc. For more on determiners, see for example http://www.quickanddirtytips.com/education/grammar/when-to-use-articles-before-nouns.
This means that your example (I saw dog yesterday) is not correct (unless dog is someones name). The correct version of your example depends on the context, but it definitely need a determiner. The following are some examples:
- I saw a dog yesterday.
- I saw the dog yesterday.
- I saw Linda's dog yesterday.
In English, singular nouns should be accompanied by some kinds of determinants before them. The article a is mainly used to inform the addressee that the word is either mentioned for the first time in the written or oral speech or the speaker/ writer means any member of a general subgroup. Consider the following examples,
Tuna is a fish.
A tall boy entered the hall. The boy was my Dad's colleague.