In contrast, Manser says, a person's passive vocabulary consists of the words whose meanings they knowâso that they do not have to look the words up in a dictionaryâbut which they would not necessarily use in ordinary conversation or writing (The Penguin Writer's Manual, 2004).
Sleep Apnea, Night Terrors, and Nightmares. Sleep apnea may also be to blame for your nightmares. During sleep apnea, your brain senses the low oxygen and realizes that you are under a very real threatâyou are being choked or smothered by your own bodyâand if nothing is done you will die.
The most common sleep breathing disorder is Obstructive Sleep Apnea (OSA), which is caused when the upper throat muscles relax too much during sleep, cutting off or restricting the airway. (1-4) These episodes, which also cause the oxygen level in the blood to drop, last from 10 seconds to a minute or longer.