Preliminary data of the biodiversity in the area VNU Journal of Foreign Studies, Vol 37, No 1 (2021) 1 18 1 RESEARCH THE CATEGORY OF VOICE IN VIETNAMESE A SYSTEMIC FUNCTIONAL DESCRIPTION Hoang Van Van* VNU University of Languages and International Studies, Pham Van Dong, Cau Giay, Hanoi, Vietnam Received 1 October 2020 Revised 5 November 2020; Accepted 12 January 2021 Abstract This article is a functional description of the category of voice – arguably, one of the most slippery notions in the gr[.]