unique

definition: 
to be the only one of a kind; special
sentence: 
Tina was a neurologist with unique compassion and curiosity; she wrote books about people whose brains behaved in very unusual ways.
difficulty: 
very easy
toefl frequency: 
3
toefl classification: 
adverb: 
uniquely
adjective: 
unique
adverb sentence: 
Her style of writing is uniquely her own.
adjective sentence: 
He was presented with a unique opportunity to attend the conference.