gamete: a mature sexual reproductive cell having a single set of unpaired chromosomes
reproductive cell: a spermatozoon or an ovum; a cell responsible for transmitting DNA to the next generation
mercury thermometer: thermometer consisting of mercury contained in a bulb at the bottom of a graduated sealed glass capillary tube marked in degrees Celsius or Fahrenheit; mercury expands with a rise in temperature causing a thin thread of mercury to rise in the tube