Before plural nouns do not add article
Do not add before abstract nouns, such as Honesty, bribery and so no specific shape, not "a" to indicate, nouns (water, food) table, although the substance is a specific thing, but the shape is not fixed, nor can the "a" to represent
When do complement proprietary name, noun proper noun when treated subject and object complement complement is true
The definite article from that / those (that) have to refer to the meaning of
Only a proper noun can be understood without The, then why unique sun Sun moon plus The?
Syntax club which has a detailed explanation: similar to "the Great Wall" "the sun" is a compound word interpreted as "very great that the wall", "the star called the sun" that is sun and moon are not unique.