Ideational Grammatical Metaphor In Scientific Discourse And Its Participation In Construction Of Knowledge

Knowledge is indispensable from language and knowledge is typically constructed by language.As the essential semantic resource,ideational grammatical metaphor can realize reconstruction of experience through remapping between semantics and lexicogrammar.Knowledge needs to be presented in the form of discourse.Scientific knowledge presented in science textbooks is uncommon sense knowledge,which is the result of reconstructing commonsense knowledge through ideational grammatical metaphor.Knowing disciplinary knowledge and disciplinary knowledge-building are equivalent to know disciplinary discourse.This study aims to reveal the linguistic features of ideational grammatical metaphor in the discourse of science textbook and the functions of ideational grammatical metaphor in knowledge-building are investigated.This study chooses the first chapter from the seventh edition of Atkins’ Physical Chemistry as research corpus.Combining Halliday’s(1996)ideational grammatical metaphor with Maton’s(2011)semantic density and semantic gravity,this study puts forward analytical framework of knowledge-building.Different ideational grammatical metaphors have been retrieved by concordance tool Antconc 3.2.1.and those that cannot be searched by the software have been identified manually.With the aid of Excel to summarize the frequency,this study discovers the linguistic features and linguistic realization forms of different ideational grammatical metaphors in the science textbook.The findings are as follows:(1)In terms of distribution,nominalization,verbalization,adjectivisation and other types have virtually occurred in the science textbook with 52%、23%、20%、0.05% respectively.It indicates that nominalization is most widely employed and proportion of verbalization and adjectivisation is relatively large.(2)The subtypes of nominalization are ranked in descending order based on the proportion: process element to entity element(68%)> quality element to entity element(29%)> relator element to entity element(0.02%)> circumstance element to entity element(0.01%).Zero element to entity element has not occurred in the science textbook.It demonstrates that process element to entity element is the most salient linguistic feature in the category of nominalization.(3)The subtypes of verbalization are ranked indescending order based on the proportion: relator element to process element(76%)>zero element to process element(21%)> circumstance element to process element(0.03%).It’s obvious that relator element to process element is extensively used.(4)The subtypes of adjectivisation are ranked in descending order based on the proportion:process element to quality element(91%)> relator element to quality element(0.06%)>circumstance element to quality element(0.03%).The proportion of process element to quality element is much higher than that of other subtypes in adjectivisation.(5)Other types include relator element to circumstance element(23%)and entity element to expansion element(76%).The results of this study show:(1)Ideational grammatical metaphor serves to construct uncommon sense entities,including metaphorical entities and technical entities.Metaphorical entity is constructed by process element to entity element and quality element to entity element,which has condensed knowledge.As for technical entity,it is realized by semantic distillation of nominalization,which has strengthened semantic density and weakened semantic gravity of the discourse.In addition,ideational grammatical metaphor can build technical taxonomy that divides technical terms into composition and classification based on semantics.Technical taxonomy enables to integrate and subsume different technical terms into theory to develop hierarchical knowledge structure.(2)Ideational grammatical metaphor is capable of establishing semantic relations between different technical terms within the clause by defining technical terms and explaining the process of shaping technical terms,which has strengthened the abstraction of discourse to improve its verticality.(3)Ideational grammatical metaphor can contribute to organizing relative knowledge into discourse to make information flow in scientific discourse.This study can help students to master the language of science and know patterns of disciplinary knowledge-building.Meanwhile,it serves to provide pedagogical implications for teaching science.