1 Introduction

The development of business discourse in terms of genre, pragmatics, and cross-cultural communication was discussed, emphasizing the importance of corporate external communication discourse in conveying information and contextual effects. The article points out that corporate promotional videos, as an important component of external communication, are favored by companies from various countries. This article takes the promotional videos of Chinese and American companies as the research object, and uses Halliday&Hasan's grammar coherence model to analyze the use of grammar coherence resources in the external business discourse of Chinese and American companies.

2. Grammar coherence theory and corporate external communication discourse

This paper discusses the multi-disciplinary research trend of enterprise publicity discourse under the "the Belt and Road" initiative, and points out the inadequacies of grammatical cohesion in the research of business publicity discourse. Coherence theory is defined as a method of connecting linguistic units and patterns, involving the association between content and semantic environment. Halliday&Hasan extended the coherence theory to promote discourse formation through "textual mechanisms", including four grammatical coherence devices: reference, substitution, omission, and connection. Reference ensures internal connections in language, substitution and omission avoid repetition, and connections reflect logical relationships in the text. Domestic and foreign scholars have conducted extensive research on grammatical coherence, mainly focusing on academic journal articles in both Chinese and English, exploring the similarities and differences in coherence between the two languages. Domestic research attempts to study grammatical coherence from the perspectives of metaphor, speech acts, and writing instruction. However, research on grammatical coherence in business discourse mainly focuses on written financial news, lacking comparative studies on grammatical coherence in dynamic external propaganda business discourse such as promotional videos. At present, research on corporate external communication discourse mainly focuses on text comparison and translation strategies, neglecting the comparative study of grammatical coherence devices.

3 Research questions and processes

This chapter is based on Halliday&Hasan's grammatical coherence model to analyze the use of four types of grammatical coherence resources in Chinese and American corporate promotional videos: reference, substitution, omission, and connection. The study aims to reveal the overall characteristics and significant differences in grammatical coherence between Chinese and American corporate promotional videos, and specifically compare the use of four grammatical coherence devices. The sample includes English promotional videos of 26 companies from the 2023 Fortune 500 in China and the Fortune 500 in the United States, and two English corpora of external business discourse for small Chinese and American companies have been constructed. The total duration of the video is 6073 seconds, with a total of 10777 characters, including 7925 symbols for Chinese corporate promotional videos and 2852 symbols for American corporate promotional videos. Convert the video into TXT text using Feishu software, and search using AntConc 3.2.4w software to calculate standardized frequency per 10000 words. At the same time, Loglikelihood and Chi square Calculator 1.0 were used to conduct a difference test on the use of grammatical coherence in Chinese and American corporate promotional videos, analyzing whether there was a statistically significant difference and conducting descriptive analysis.

4 Research Results and Discussion

In a comparative study of the ability of Chinese and American companies to use grammatical coherence in their external publicity discourse, the research results show that the use of grammatical coherence in American corporate promotional videos is higher in both quantity and variety than in Chinese companies, and there is a significant difference. Chinese companies tend to use connections and referents, while American companies prefer referents and connections. The frequency of substitution and omission is relatively low in both, with a particularly significant difference in the use of omission. The frequent use of conjunctions such as "and" in promotional videos of Chinese and American companies helps to express logical relationships clearly. The use of referential language is more common in American corporate promotional videos, and both Chinese and American companies tend to use "we" to refer to the overall company and shorten the distance with consumers. American companies often use "I" to highlight personal preferences. There are significant differences in the use of alternative language between China and the United States, with American companies being more adept at using alternative language for business promotion, mainly related to their brand and products. The use of ellipsis is more common in American corporate promotional videos, while it is less commonly used by Chinese companies to adapt to the language comprehension abilities of different audience groups. The use of omission helps to save promotional costs, enhance discourse rhythm, and avoid semantic repetition.

5 Conclusion and Implications

Research shows that the frequency and flexibility of grammatical coherence in promotional videos of American companies are higher than those of Chinese companies, with significant differences. Chinese corporate promotional videos tend to use conjunctions, while American companies prefer referential language, both of which use less ellipsis. The frequent use of conjunctions such as "and" can strengthen the logical relationship of external communication discourse, enhance brand and product professionalism. The frequency of reference language used by Chinese companies is lower than that of American companies, and there is a significant difference. Suggest incorporating grammar coherence into business English teaching to enhance students' awareness of grammar coherence.