The substance that men ejaculate during an orgasm. For a "normal" man, the event will contain over 80 million sperm. In addition to the little wiggly things, semen contains (taken from several web sites):
  • water
  • aboutonia
  • ascorbic acid (vitamin C)
  • blood-group antigens
  • calcium (yes, just like milk!)
  • chlorine (add your own little contribution to the cleanliness of that hot tub!)
  • cholesterol (I'm not sure if this is "bad cholesterol" or "good cholesterol")
  • citric acid, creatine, deoxyribonucleic acid, fructose, glutathione, hyaluronidase, inositol, lactic acid, magnesium, nitrogen,
  • phosphorus and potassium (what do you know, these are good for fertilization too!)
  • prostaglandins (fatty acids that, while not a hormone, perform hormone-like functions)
  • purine, pyrimidine, pyruvic acid
  • sodium (good to have, especially if you've been sweating a lot)
  • sorbitol, spermidine, spermine,
  • urea, uric acid, (okay, that doesn't sound great)
  • vitamin B12 and zinc (you would think this is a multivitamin).

Sources: merriam-webster.com, thriveonline.com, http://www.ivf.com.au/sperm/SfSComposition.html