alternation

definition: 
the action or process of altering or being altered.
sentence: 
The natural alternation of day and night play an important role in the lives of many ocean creatures
difficulty: 
easy
toefl frequency: 
2
toefl classification: 
adverb: 
alternably
adjective: 
alternable
adverb sentence: 
adjective sentence: 
verb: 
alter
verb sentence: 
Our outward appearance alters as we get older
noun: 
noun sentence: