Let V be a vector space over a field F = (F, +, .), F* = F\{0}, LF(V)the semigroup of all linear transformations of V into itself under composition, and Mn(F) the multiplicative full n × n matrix semigroup over F. In this paper, it is proved that the semigroup Mn(F) has a proper dense subsemigroup if and only if(F*, .) has an element of infinite order. Also, the semigroup LF(V) has a proper dense subsemigroup if and only if dimF V = ∞ or (F*, .) has an element of infinite order.