The term 'hour' can be defined in many ways, and each of the following crossword solutions provides a unique definition. A PERIOD is a length of TIME that is usually measured in hours, and a MOMENT is an instant or brief interval of TIME. An OPPORTUNITY is a favorable juncture of circumstances, and TIME is a nonspatial continuum in which events occur in apparently irreversible succession. ZERO is the absence of any quantity or magnitude, and HAPPY is a feeling of pleasure or contentment.