Origin of the word Carat
The word carat comes from the Carob Mediterranean tree whose seed was used for centuries as the standard of weighing precious gems. Each carob seed weighs approximately one-fifth of a gram. A carat is one-fifth of a gram.
A blemish is a locational term, which is to say a blemish is found on the outside of a gem, whereas inclusions are located inside a gem. Blemishes occur after a diamond’s formation, during the cutting, mounting, and wearing of a polished diamond. Extra facets, polish lines (thin parallel grooves and ridges) or burns (from excessive heat on the polishing wheel during cutting) are examples of blemishes introduced during the manufacturing process. Nicks, scratches, chips and abrasions are examples of blemishes introduced during the handling, mounting or wearing of a diamond. Chips are shallow openings where part of the diamond was broken off, most often at the girdle edge.
Sources for these definitions are GIA.edu, Google.com, Meriam-Webster.com, and Wikipedia.org.