maintain

definition: 
keep in a certain state, position, or activity
sentence: 
The genetic factors that explain why some people seem to maintain healthy lungs despite a lifetime of smoking have been uncovered by scientists.
In the job search process, the number of connections we maintain in our professional and personal networks is often critical.
difficulty: 
very easy
toefl frequency: 
3
toefl classification: 
adverb: 
adjective: 
adverb sentence: 
adjective sentence: 
verb: 
maintain
verb sentence: 
noun: 
maintenance
noun sentence: 
Proper maintenance of a car's engine will preserve its performance and value.