Webster's New World Medical Dictionary

homologous 1
Similar in appearance, form, or
function.
2
Paired or matched; usually referring
to the relationship between two chromosomes that
are paired and so are homologs of each other.
homologous chromosomes
A pair of chromo-
somes that contain the same gene sequences, each
derived from one parent.
homology
Similarity in DNA or protein
sequences between individuals or between species.
homosexual 1
A person who is sexually attracted
to persons of the same sex. Colloquially known as
gay.
2
The act or habit of same-sex attraction.
homosexuality
Sexuality directed toward some-
one of the same sex.
hookworm
An intestinal parasite that infests a
billion people, mainly in tropical and subtropical
areas. Infection is from contact with soil contami-
nated by hookworm larvae. First signs are itching
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and rash at the site where the larvae penetrate the
skin. This is followed by diarrhea, intestinal cramps,
pain, anorexia, weight loss, and anemia. Loss of
iron and protein due to hookworm can retard the
growth and mental development of children, some-
times irreversibly. The infection can be fatal, partic-
ularly for infants, pregnant women, and persons
who are malnourished. See also 
Necator ameri-
canus.
horizontal
Parallel to the floor. A person lying on
a bed is considered to be in a horizontal position.
See also Appendix B, “Anatomic Orientation
Terms.”
hormone
A chemical substance produced in the
body that controls and regulates the activity of cer-
tain cells or organs. Many hormones are secreted by
special glands, such as thyroid hormone produced
by the thyroid gland. Hormones are essential for
every activity of life, including the processes of
digestion, metabolism, growth, reproduction, and
mood control. Many hormones, such as neuro-
transmitters, are active in more than one physical
process.