The following are some terms that have been known to confuse people.  This
list is by no means complete or comprehensive.

Amelanistic: "Albino" in the conventional sense; lacking all black pigment.
This is a widespread mutation in several species.  Amelanistic animals are
often red or yellowish, instead of white like albino mammals; this is because
amelanism does not affect the red and yellow pigments, or indeed any pigments
other than melanin.

Anerythristic: "Black albino"; lacking red pigment.  Anerythristic animals
are typically black and white.  This is a common mutation in corn snakes, and
has also emerged in several other snake species.

Anuran: A frog or toad.  (There is no tightly defined distinction, though
members of the genus _Rana_ are sometimes called "true frogs" and members
of the genus _Bufo_ "true toads".)

Axanthic: Lacking yellow pigment.  Axanthism produces a "black albino"
effect in certain species whose dominant pigments are yellow.

Axolotl: A species of salamander (_Ambystoma mexicanum_) which normally does
not metamorphose into a terrestrial form, instead remaining in an aquatic
larval stage throughout its life.  Axolotls were formerly thought to be
unmetamorphosed tiger salamanders (_Ambystoma tigrinum_), and some older books
describe them as such.

Boid: A boa or python.  (Two syllables, accent on the first, with a long 'o';
this word is derived from "boa".)

Brumation: A term intended to describe "hibernation" in reptiles and
other cold-blooded animals.  The point of having two terms is simply that
hibernation is a complex process involving some regulation of body
temperature, whereas brumation is a simpler general slowing of all
metabolic processes.  The word is a fairly recent coinage (1965, in a
paper by Mayhew), and it is reported to be falling out of usage among
academic herpetologists.  It's probably fine to just say "hibernation".

Caecilian: A member of the order Gymnophiona (formerly Apoda), an order of
elongated, eellike or wormlike amphibians.  The most familiar is the "rubber
eel", sometimes sold in aquarium stores.

Caudal: Pertaining to the tail.

Caudata: The order of amphibians comprising salamanders and newts.

Colubrid: A member of the "typical snake" family: king snakes, rat snakes,
corn snakes, garter snakes, and in general most of the snakes that readers
outside Australia encounter frequently.

Crepuscular: Active at dawn and dusk.  This describes many herps, especially
snakes.

Elapid: A member of a large family of venomous snakes with fangs set in the
rear of their mouths, including cobras, coral snakes, a majority of Australian
snakes, and many more.

Fossorial: Burrowing.

Gravid: The right word to use instead of "pregnant" when you're talking about
eggs.  Note that all reptiles reproduce via eggs; if they give live birth,
it's because the eggs hatch internally.  In consequence, there is no such
thing as a pregnant reptile; the word is always "gravid".  (However, rumor
holds that some of the more evolutionarily advanced snakes have been found
to have primitive placentas, which would actually make the term "pregnant"
more appropriate.)

Herp/Herptile: Generic terms for reptiles and amphibians; see question 4.3.
The word "herptile" is a fairly recent coinage with no real etymology, and some
people object to it (the phrase "linguistic abomination" has been used).
Recently the use of "herpetofauna" has been suggested as a more
scientific term - but within the group "herptile" is a perfectly
understandable and acceptable term.

Heterozygous: A proper definition of this term requires a quick primer in
genetics, which is definitely beyond the scope of this FAQ.  Briefly, saying
that an animal is "heterozygous for amelanism" means that it carries the
gene that causes amelanism, and can pass that gene on to its offspring, but
it is not itself amelanistic (having inherited a "normal" gene that suppresses
the amelanistic gene).

Pipping: The stage in the hatching process in which a hatching snake makes a
preliminary slit in the eggshell with its egg tooth.  The term has also been
used to describe the process of making an artificial slit in the egg to help
the hatchling emerge (this practice is widely discouraged except in unusual
circumstances).

Ranid: One of the "true frogs" of the genus _Rana_.  The genus includes
the majority of the hoppy, bank-dwelling animals that most of us think of as
typical frogs, but excludes tree frogs, toads, and many others.

Salienta: An obsolete name for the order Anura (frogs and toads).

STV: Snout-to-vent (length).  This is the usual way to measure an amphibian or
lizard (the point is that it's inconvenient and somewhat misleading to include
the legs of a frog or the tail of a lizard or salamander in its length).

Urodela: An obsolete name for the order Caudata (salamanders and newts).

Vent: The cloacal opening (location of the urinary and genital organs),
especially on a snake's belly.  In snakes and caecilians, the vent is the
official boundary between body and tail.  (Actually, this is equally true of
lizards and limbed amphibians, which, however, usually have other indicators
as well---i.e., legs!)

Viperid: A member of the stereotypical family of venomous snakes, including
rattlesnakes and almost anything with "viper" in its name.  Viperids have
large fangs mounted in the front of the mouth and have a tendency to be
stocky snakes with a certain stereotypical head shape (however, it's not
safe, of course, to decide that a snake isn't venomous because "it doesn't
have a viper head").