Are Espadas, Vasto Lorde(s)?

I've been wondering whether espadas are vasto lordes. coz i remember there's few parts in the series about vasto lordes and they don't seem to appear at all. there's one part during the flashback of neliel's memories. she said that aizen-sama wanted her and nnoitora to find for vasto lordes. and seriously i still dont know whether espadas are vasto lorde(s) or not.