valid

definition: 
having a sound basis in logic or fact; reasonable
sentence: 
I don't have a valid reason for missing the class.
difficulty: 
very easy
toefl frequency: 
3
toefl classification: 
adverb: 
adjective: 
adverb sentence: 
adjective sentence: 
verb: 
verb sentence: 
noun: 
validity
noun sentence: 
The professor questioned the validity of the test results