To list initialize a vector of strings, we must supply values that can be used as strings. In this case, there is no confusion about whether to list initialize the elements or construct a vector of the given size

vector<string> v5{"hi"}; // list initialization: v5 has one element
vector<string> v6("hi"); // error: can't construct a vector from a string literal
vector<string> v7{10}; // v7 has ten default-initialized elements
vector<string> v8{10, "hi"}; // v8 has ten elements with value "hi"