spontaneous

definition: 
unplanned; uncontrolled
sentence: 
Because of spontaneous mutations in germ cells — sperm and eggs — each generation of our species is subtly different.
The spontaneous combustion inside the cylinder creates the power of the motor.
difficulty: 
easy
toefl frequency: 
2
toefl classification: 
adverb: 
spontaneously
adjective: 
spontaneous
adverb sentence: 
adjective sentence: 
verb: 
verb sentence: 
noun: 
spontaneity
noun sentence: