Consider light incident on a thin film and reflected by both the upper and lower boundaries.

It is not just Mr. Follett's stories that are unfettered by national boundaries.

Act as spatial regulators for the organ identity genes by defining boundaries for their expression.

Each Corps had an assigned sector, by boundaries, that it could operate within.

Flying across bush Alaska, the entire landscape was a seamless whole, unmarred by man-made boundaries.

The dragon is prevented from leaving the desert by actinic boundaries.

This was an attempt to end, or at least limit, intertribal warfare by defining boundaries between tribal territories.

Science and scholarship thrive on exchanges of information unimpeded by national boundaries.

Others divide by county lines or watershed boundaries.

Everything would convert instandy to the correct denominations, as determined by the various countries and economic boundaries.