continuum

A continuous series or whole, no part of which is noticeably different from its adjacent parts, although the ends or extremes of it are very different from each other.

Near-synonym: spectrum

So, the white line implies Blacklessness and the black background implies Whitelessness – that is, once the white line, a continuum, has emerged from blackness, also a continuum, and the two continua engage in an “inter-penetrative” (Buddhist term) process.

A continuous extent.

A doorknob of whatever roundish shape is effectively a continuum of levers, with the axis of the latching mechanism—known as the spindle—being the fulcrum about which the turning takes place.

The nondenumerable set of real numbers; more generally, any compact connected metric space.

A touch-sensitive strip, similar to an electronic standard musical keyboard, except that the note steps are ¹⁄₁₀₀ of a semitone, and so are not separately marked.