Webster's New World Medical Dictionary

evolution
The continuing process of change.
evolution, biologic
See 
biologic evolution.
evolution, cultural
See 
cultural evolution.
evolutionarily conserved gene
A gene that has
remained essentially unchanged throughout evolu-
tion. Conservation of a gene indicates that it is
unique and essential: There is not an extra copy of
that gene with which evolution can tinker, and
changes in the gene are likely to be lethal.
evolutionarily conserved sequence
A base
sequence in a DNA molecule (or an amino acid
sequence in a protein) that has remained essentially
unchanged throughout evolution.
Ewing sarcoma
See 
sarcoma, Ewing.
exacerbation
A worsening. In medicine, exacer-
bation may refer to an increase in the severity of a
disease or its signs and symptoms. For example, an
exacerbation of asthma might occur as a serious
effect of air pollution, leading to shortness of breath.
exaggerated startle disease
See 
hyperex-
plexia.
exam, pelvic
See 
pelvic exam.
exam, rectal
See 
digital rectal exam.
exanthem
A rash on the outside of the body. By
contrast, a rash on the inside of the body (for exam-
ple, inside the mouth) is called enanthem. A patient
with measles can have both exanthem and enan-
them. See also 
enanthem; measles; rash.
exanthem subitum
A sudden rash. See also
measles.
excess iron
An overload of iron that can damage
the heart, liver, gonads, and other organs. See also
iron excess.
excise
To cut out entirely. For example, a scalpel
or laser beam may be used to excise a tumor. The
terms excise and resect are not synonymous. Excise
implies total removal, whereas resect does not.