This study intends to investigate the way of formation of ``N-sanyang`` compound words, and expansion of ``sanyang``s meaning, focusing on ``N-sanyang`` construction. If N1 is an instrumental argument, a ``N-sanyang`` construction can be analyzed as a compound word. However if N1 is a thematic argument, it can be analyzed as a syntactic construction based on three criteria. Three criteria are a possibility of corresponding with a syntactic construction, a degree of productivity, and expansion of ``sanyang``s meaning. If N1 is a thematic argument in a ``N-sanyang`` construction, ``N-sanyang`` construction is basically analysed as a syntactic construction. However, that ``N(theme)+sanyang`` which have a third meaning can be considered as a compound word. It can be listed on the lexicon by the expansion of meaning. What is more ``N-sanyang`` words which N is a thematic argument are widely used than before. That phenomenon are based on the expansion of meaning of sanyang as time goes by.