Webster's New World Medical Dictionary

TVS
Transvaginal ultrasound.
twin
One of two children produced in the same
pregnancy. Twins can develop from one ovum (egg)
or from two ova (eggs). Twins who develop from a
single ovum are called monozygotic or identical
twins. They have identical genomes. Twins who
develop from two ova that are fertilized at the same
time are called dizygotic or fraternal twins. They are
nonidentical and have different genomes.
tympanic membrane
The eardrum, a thin mem-
brane that serves as a partition between the external
ear and the middle ear and transmits the motion of
sound waves to the chain of bones in the middle ear.
tympanites
See 
tympany.
tympano-
Prefix indicating a relationship to the
eardrum (tympanic membrane), as in tympanome-
try (a test that measures the function of the middle
ear).
tympanometry
A test that measures the function
of the middle ear. Tympanometry works by varying
the pressure within the ear canal and measuring the
movement of the eardrum (tympanic membrane).
tympanoplasty
A surgical operation to correct
damage to the middle ear and restore the integrity
of the eardrum.
tympanostomy tube
See 
ear tube.
tympanum
The cavity of the middle ear, which is
separated from the outer ear by the eardrum.
tympany
A hollow drum-like sound that is pro-
duced when a gas-containing cavity is tapped
sharply. Tympany is heard if the chest contains free
air (pneumothorax) or the abdomen is distended
with gas. Also known as tympanites.
type I error
See 
alpha error.
type 1 GM2-gangliosidosis
See 
Tay-Sachs
disease.
type II error
See 
beta error.