The saliva is a viscid, watery fluid that is secreted from the salivary glands. The secretions from the individual salivary glands have their own special characteristics, and these are not the same in all animals. In humans, the saliva is a more or less turbid and slightly viscid fluid, generally of an alkaline reaction, and is secreted by all three of the salivary glands, namely parotid, submaxillary, and sublingual glands.
Human saliva consists of 99.5% water. The remaining percentage is comprised of electrolytes (e.g. sodium, potassium, calcium, magnesium, chloride, bicarbonate, phosphate, iodine), mucus, enzymes (e.g. ptyalin, lingual lipase, kallikrein, etc.), secretory immunoglobulin A, lysozyme, white blood cells, and epithelial cells. The saliva moistens the mouth and food, aids in swallowing, and starts the digestion of starches. It is a thick transparent liquid rich in digestive enzymes like ptyalin (salivary amylase) used to break down foodstuff.
Some animals have other use for their saliva. For example, swifts (family Apodidae) use their saliva to build nest. Venomous animals such as cobras and vipers have venomous saliva that they use for hunting and disabling their prey (as well as foes).