beak

definition: 
A bird’s horny projecting jaws; the horny projecting jaw of animals other than birds, for example a turtle or squid.
sentence: 
As a trombone player pulls in the slide to make a higher frequency sound by reducing the volume of the tube, so does a bird open its beak and pull back its head to reduce the volume of its vocal tract.
difficulty: 
easy
toefl frequency: 
2
toefl classification: