Junction, n.
Etymology: [L. junctio, fr. jungere, junctum, to join: cf. F. jonction. See Join.]
1. The act of joining, or the state of being joined; union; combination; coalition; as, the junction of two armies or detachments; the junction of paths.
2. The place or point of union, meeting, or junction; specifically, the place where two or more lines of railway meet or cross. Junction plate (Boilers), a covering or break-join plate riveted to and uniting the edges of sheets which make a butt joint. -- Junction rails (Railroads), the switch, or movable, rails, connecting one line of track with another.
Shades of meaning
Fernald has no entry of its own for junction; he lists it under union.
He lists it without comment; the entries above explain its neighbors.