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.
Apnea, which is when airflow is completely blocked and breathing stops for at least 10 seconds. Hypopnea, which is when airflow is 50% decreased for at least 10 seconds, or there is a 30% decrease in airflow with a subsequent awakening or serious drop in oxygen saturation levels.