predecessor

One who precedes; one who has preceded another in any state, position, office, etc.; one whom another follows or comes after, in any office or position.

I thought about my predecessor, who had died of drink and smoke; and I could have wished he had been so good as to live, and not bother me with his decease.

"The Northern Heights at last," you say to yourself, hastily closing the carriage window because the Yorkshire coal used by the Eastern Region and its predecessors makes their tunnels more sulphurous than any we know.

A model or type of machinery or device which precedes the current (or later) one. Usually used to describe an earlier, outdated model.

The steam engine was the predecessor of diesel and electric locomotives.

No. 6959 is painted in the standard wartime black livery and, like its immediate predecessors, does not carry a nameplate, but the words "Hall Class" have been painted on the middle coupled-wheel splasher.

A vertex having a directed path to another vertex