A security blanket is a blanket given to an infant soon after birth, and put into their bed with them night after night. The child sleeps with the blanket wrapped in their arms until it becomes as much a part of the child's Going to Sleep ritual as the goodnight kiss from mum, the dim light, the bed itself.

A security blanket is generally soft, and quite often fluffy. It is often rubbed against the nose as the child wanders toward sleep.

If the Special Blanket is lost, or misplaced, or stolen (by the child's wicked mother in order that it may be washed), and not found by bedtime, it is likely that no one in the house will sleep until it is in its rightful place, in the child's arms. And don't think you will get away with buying two identical blankets especially in order to compensate for problems like this. The Child Will Know

And weep

And refuse to be comforted. 

For many, many hours.

Most children forget their blanket as time goes on. By the time they begin school, most children will have left their special blanket behind, to be remembered only by their mothers who wash it one last time, fold it carefully, and keep it in a box of treasures, never to be seen again - at least until the child's 21st birthday party when it will have a special place amid the embarrassing photographs, amusing clothes, and "cute" sayings of the child's youth.