junctions

A junction is a point or place where two or more things meet, join, or diverge. The term is applied across many disciplines to denote a connection, boundary, or transition where elements interact or exchange.

In transportation, a road or street junction is where two or more routes come together. These can be simple at-grade intersections or more complex grade-separated interchanges with ramps and overpasses. Railway junctions are locations where lines converge or diverge, allowing trains to switch tracks or routes.

In electrical engineering and electronics, a junction refers to a point where conductors meet, such as a junction box that houses electrical splices. In semiconductor technology, a pn junction is the boundary between p-type and n-type material and is fundamental to the operation of diodes and transistors.

In biology, cellular junctions connect neighboring cells and regulate communication and adhesion within tissues. Notable types include tight junctions, which form barriers; gap junctions, which enable direct intercellular communication; and desmosomes, which provide mechanical strength. Neural synapses are functional junctions where signals are transmitted between neurons or between neurons and other cells.

In other contexts, junctions can describe nodes in networks or graphs where multiple pathways meet, or joint points in plumbing or piping systems where different sections are connected. Across these uses, a junction conveys the essential idea of a converging or boundary point that links separate elements.