The present invention provides a hollow fiber, which includes: at least one thermoplastic polymer with an equilibrium water content of 2% or less; wherein the number of hollow portions (.alpha..sub.1) and a hollow ratio (.alpha..sub.2) in said fiber satisfy the following equations: .alpha..sub.1.gtoreq.7 2.ltoreq..alpha..sub.2.ltoreq.65 0.14.ltoreq.(.alpha..sub.1.times..alpha..sub.2)/100.ltoreq.250. Other embodiments of the present invention include articles containing the hollow fiber, methods of making and of using, and a sea-island conjugate fiber