Runs taken from within a longer sequence, keeping their order. A subsequence is a selection that respects the original arrangement.
Latin subsequi (to follow close behind), from sub (close to, under) + sequi (to follow); a run taken from within a longer sequence keeps the order the Latin verb already implied, nothing follows out of turn.
Runs taken from within a longer sequence, keeping their original order. A selection that respects the arrangement it was drawn from rather than reshuffling it.