Theory:

Meanings of difficult words from the lesson "The Wonder Called Sleep":
 
S.No
Words
Meanings
1
SleepA condition where one's body and mind go into relaxation mode, that typically recurs for several hours every night
2
RecoverReturn to a normal state of health, mind, or strength
3
FatigueExtreme tiredness resulting from mental or physical exertion or illness
4
AlertAble to think clearly and act promptly
5
ConsciousnessThe state of understanding and realizing something
6
REMAbbreviation for 'rapid eye movement'; quick movements of the eyes that happen at certain times while you are sleeping and dreaming
7
SinkTo move lower and deeper
8
TemperatureThe measured amount of heat in a place or in the body
9
ProbableLikely to happen or be the case
10
RevealMake known to others
11
A great dealA large amount of
12
UnfathomableIncapable of being fully explored or understood
13
WindingMove in or take a twisting or spiral course
14
Lights OutThe title of the poem; signifies bedtime when the lights are to be extinguished for the night