Complete the following statements with proper words or expressio

Complete the following statements with proper words or expressions according to the course book.​The world has about 3000（some put it 5000） languages, which can be grouped into roughly 300 language families on the basis of similarities in their basic word stock and ( ).
【正确答案】：GRAMMAR
【题目解析】：据估计, 世界上约有 3000多种(有人认为有5000种)语言。这些语言可以根据他们的基本词汇和语法的相似性大致划为300个谱系。