当可数名词单数表示泛指的含义时,其前面应有不定冠词 a(an),但是在某些特殊的结构中 a(an)往往被省去。1.在一天三餐饭前,例如:They had breakfast at 7 o’clock.他们在七点钟吃午饭。They went to their aunt’s house for supper.他们去他们的姑母家吃晚饭。2.在平衡结构中,往往两个单数可数名词由介词或连词以及词组并连。例如:They sat in the living room face to face. When the countable noun singularity represents the meaning of the generalized sign, there should be an indefinite article a(an) in front of it, but in some special structures a(an) is often omitted. 1. Before three meals a day, for example: They had breakfast at 7 o’clock. They had lunch at seven o’clock. They went to their aunt’s house for supper. They went to their aunt’s house for dinner. 2. In a balanced structure, often two singular countable nouns are joined by prepositions or conjunctions and phrases. For example: They sat in the living room face to face.