A monocular is a miniature, low powered telescope or spotting scope which you hold in your hand like a binocular but use with one eye like a telescope. A monocular shares characteristics with both binoculars and spotting scopes, but is much smaller than either. Size, then, is really what a monocular is all about. Some monoculars are no larger than your thumb or thicker than a good ink pen and any monocular will slip easily into a pocket or a purse. When a spotting scope or a binocular, even a compact, is too large to take along, there is always a monocular. There is no excuse for leaving home without your monocular.