Kijun-sen

One of the five lines that make up the Ichimoku system, conventionally translated as the base line or standard line. It is computed as the average of the highest high and the lowest low over its window, which is a midpoint of a range rather than an average of closes: it therefore has no relationship to a moving average beyond superficial resemblance, and two charts can produce the same closes and a different Kijun.

Two properties follow directly from that construction and both are visible on any chart carrying the system. The line is flat for long stretches, because the extremes of a window change only when a new extreme prints or an old one drops out of it, so it steps rather than curves. And it ignores where price spent its time inside the range entirely, since only the two extremes enter the calculation.

Its shorter counterpart is the Tenkan-sen, computed the same way over a shorter window, and the relationship between the two is what the system's traditions read: a crossing, the distance between them, and the flat sections where the base line acts as a reference other traditions would call a level. The default window lengths are conventions from the system's original publication rather than results of any test.