The Bible (probably an English translation, like the King James’) uses the word “kind,” as in Noah took two of each kind into the Ark. At least this is the English translation of a Hebrew word and Creationists have used this word as some sort of synonym for species. Creationists claim that God1 created each kind of organism and each is fixed and immutable. One kind does not evolve into another kind, this seems to be the closest to a definition that you can get. Some Creationists have accepted that some evolution does (or did) occur. They will accept that a small bit of change can occur (something like what evolutionists call microevolution) within a “kind” so that each kind may more perfectly fit its environment. God, or the Designer, has permitted this variability for the benefit of His/Its creation.
However, one kind still cannot evolve into a different kind (what some evolutionists think of as macroevolution). This is where things get confusing, Creationists never clearly define “kind,” beyond one kind cannot evolve into another kind. This is unlike scientists who do try to define “species” and are constantly discussing it, and use it fairly consistently. You cannot test their claim that “kinds” do not evolve into another kind because they do not define the term or use it in a consistent manner from which one can construct a definition. The only consistent thing seems to be that humans are one “kind” and apes are another.
“Kind” does seem to be used as a synonym for species and a kind can evolve enough to be called a subspecies. But if you start discussing real life examples (e.g. Darwin’s finches, lions and tigers, horses and zebras) maybe “kind” is not species but genus which can change enough to be a new species within a the genus. The genus Equus evolved into Equus caballus, E. burchelli, E. zebra, and E. asinus, etc.). Or maybe it is a family like the Felidae, the cat family. Felines include at least 37 species in four genera.2
Kind is used in a relative way: relative to how much evolutionary change has to be accepted, the “kind” expands or contracts so that no matter how much change there is it is only within the confines of a “kind,” never one “kind” evolving into another “kind.” With the proviso I mentioned above that apes are always a different kind than humans, who are always a separate “kind” from all other organisms. Even if the “kind” is a family level (i.e. cats/Felidae) and includes as much or more difference as in the Ponginae family—the apes—gibbons, siamangs, orangutans, gorillas, bonobo, chimpanzees, and (to some scientists) man. Others prefer to put the orangutans, gorillas, bonobo, and chimpanzees, in Homininae, with man. And of course. there all those fossil species. Kind is used in a rather amorphous way that prevents it being of any use, except to avoid being pinned to a single concept that is indefensible without admitting to there being evolution.
1 Intelligent Design proponents and Creation Scientists claims that a “designer” created each kind. But “designer” is a linguistic subterfuge to avoid be called a religion based theory. But make no mistake they are talking about God: a Christian, Biblical God.
2 Felis—the small cats: wild cats, domestic cat, lynx, bobcat, puma, caracul, etc.; Neofilis—the clouded leopard; Panthera—the big cats: snow leopard, tiger, leopard, lion, and jaguar; and Acinonyx—the cheetah. Then there are the extinct cats: the saber-tooth Smilodon, Machairodus , Homotherium Megantereon, etc.