Buffy - B'fi
the matriarch of the pod; the alpha female
B'fi has tawny, golden brown scales and pale hair. Her eyes are golden.
Dawn - D'wa
the younger sister to B'fi, beta female
Willow - W'lo
a sub-female in the pod
Tara - T'ar
a sub-female in the pod
Harmony - H'ar
a sub-female in the pod
Lilah - L'il
a sub-female in the pod
Anya - A'yo
a sub-female in the pod, tends to be somewhat possessive of X'an
Joyce - J'yc
a youngling in the pod
Riley - R'li
the dominant male in the pod, mated to B'fi; the alpha male
R'li has brown scales and short brown hair. His eyes are hazel.
Giles - G'lis
an elder of pod, Keeper of knowledge
Ethan - E'ta
an elder of pod
Gunn - C'es
an elder of pod
Graham - G'ra
an elder of pod
Wesley - W'es
a sub-male in the pod, in training as the next Keeper of knowledge
Oz - D'os
a sub-male in the pod, tends to be a loner
D'os has blue scales and hair, with a red stripe down the center of both. His eyes are bright green.
Xander - X'an
a sub-male in the pod, thought to be somewhat odd
X'an has shimmering blue scales and green hair. His eyes are amber ringed with deep gold.
Angel - A'nil
was previously the dominant male of another pod, is now an Outsider
A'nil has mottled blue & gray scales and blue-gray hair. His eyes are dark, almost black.
Penn - P'en
a son of A'nil, is now an Outsider
P'en has yellow scales and light brown hair. His eyes are dark, almost black.
Drusilla - D'ruc
a son (yes, son!) of A'nil, is now an Outsider
D'ruc has orange scales and dark brown hair. His eyes are dark, almost black.
Spike - S'ke
a son of A'nil, is now an Outsider
S'ke has rich red scales and deep black hair. His eyes are blue with flecks of silver.
Darla - D'la
a sub-female in A'nil's former pod, mother of P'en and D'ruc.
Cordelia - C'or
a sub-female in A'nil's former pod, mother of S'ke. Killed in a shark attack soon when S'ke was a youngling..
Lindsey - L'in
from one of the stories G'lis tells, L'in was a sub-male from a pod who became an Outsider
The matriarch is the head of the pod. She is the alpha female. Her mate, the male who courts and wins her during the yearly mating season, is the alpha male. While the matriarch remains the alpha female during her lifespan, the alpha male only remains as dominant male as long as he continues to win the matriarch during courtship. Should another male's challenge prevail, he would supplant the former alpha male until the next mating season.
Elders of the pod are those merfolk who have lived for a while and gained the experience necessary to be considered an 'adult'. The Keeper is generally considered the wisest of the elders due to his/her training and knowledge of what has gone before.
Sub-males and sub-females are pretty much the 'teenagers' of the pod. They are not younglings, but are not yet considered adults.
Outsiders are those merfolk who do not belong to a specific pod, either by choice (loners), force (rogues), or perhaps due to a calamity befalling the majority of the pod. Many pods are hesitant to accept Outsiders at first, but it is possible to join a new pod. As in any society, some pods are more accepting than others.
Merfolk have a keen sense of taste and 'smell' (using their tongue the way a snake would) and decent eyesight. Their hearing is also quite good, and they have the ability to hear sonar frequencies, similar to the way dolphins and whales do.
Merfolk have sharp teeth and claws, which are used to hunt and devour their prey. They are omnivores, eating both fish and other sea creature as well as types of sea growth. Merfolk also have fins on their 'thighs' and biceps, as well as sharp spines alone their forearms and hips and a row of shorter spines down their backs. These spines contain a venom capable of paralyzing small prey, but barely affecting larger creatures. The spines normally lay down flat unless the mercreature is angry/scared/provoked/defensive, in which case the spines hackle threateningly.
Merfolk have gills on the sides of their 'waists', used to help breath under water. Their lungs are also capable of filtering oxygen out of water, as well as being usable in normal air.
Males have internal genitals, which extend from a nearly invisible slit when they are aroused. Female genitals are normally not very visible unless the female is in heat. Then, the genitals 'pout' open in invitation, releasing very strong pheromones in order to attract suitors. Most males find this unbearably arousing.
The anal opening on merfolk is located a few inches below their genital slits.
Thanks to Argo for the idea that I should explain these sorts of things a bit more clearly. I may add other points of clarification as the story progresses. More descriptions will also be added as they develop.