A life form is any living entity.
Because there is such a vast multiplicity of life forms inhabiting the cosmoi, various schemes have been devised to try to classify them in a useful manner into defined categories. By far the most widespread and well developed is one particular system of taxonomy. While on True Earth generally credited to an eighteenth-century scientist named Carl Linnaeus, this system appears to be panyparic, having arisen seemingly independently on many worlds, albeit in some cases with some slight variation.
Standard biological taxonomy involves the use of groupings of life forms, known as taxa, on various levels, with those on higher levels potentially including multiple lower-level taxa. The lowest-level standard taxon is that of the species, though some species are divided further into subspecies and possibly beyond. Species are grouped into genera, genera into families, families into orders, orders into classes, classes into phyla, phyla into kingdoms, kingdoms into empires, empires into fœdera, and fœdera into universes. The universe, the highest-level taxon, represents (in theory, at least) an entirely different way for life to arise.
The word "creature" is sometimes used synonymously with "life form", but given its etymology many etorists prefer to reserve this word for beings made artificially by magical and technological means. There are other words for living entities that are often misunderstood by etorical laymen but which, in general, are more specialized. An organism, for instance, is a living thing that arose by a process of natural evolution by natural selection (that is, of the universe Biota), or which has been transformed from such a life form. An animal is even more restrictive, referring to a particular kingdom of organisms. A race is an ellogous species of life form, one capable of sophisticated abstract thought.
There are other words, such as "beast", "florum", and "faunum", that are somewhat more vaguely defined. "Florum" and "faunum" refer respectively to plant-like and animal-like entities, that is, life forms that are generally sessile and living off their nonliving environment, and life forms that move about and feed on other life forms. These terms come from etymologically iffy back formations from the collective terms "flora" and "fauna", and still are not universally accepted, but are becoming increasingly widely used in the general etorological community, though not yet on True Earth. The word "beast" can be used to refer to any alogous fauna, though it is often used figuratively to refer to ellogous life forms of particularly savage or unthinking mindset.
The study of life forms in general is called "etorology", or sometimes simply "etory". Again, there are more specific terms for scientists studying life forms of particular taxa, or within given environments. The study of biotic organisms in particular is called "biology"; sometimes this term is used synonymously with "etorology", and "eubiology" is used for the more specific study of organisms, but this is becoming increasingly rare. The study of life forms made or animated by magic (that is, pertaining to the universe Mira) is called "phasmology". The study of seins and other artificial life forms created through technology (creatures of the universe Machillae) is called "threptology". The study of prehistoric life (especially prehistoric organisms, but more broadly prehistoric life in general) is called "palaeontology". The study of microscopic life forms is called micretory. The study of a life form's changes during its development is called ontogeny, that specifically of its physical growth auxology. The study of the internal structure of living things (again, especially of organisms) is called anatomy. The study of cyclical phenomena in life forms' behavior and life cycles is called chronobiology. Etorical taxonomy is the study of the classification of living beings, and ecology of how they interact with each other and with their environment.
Comparative etorists with broad knowledge of life on many worlds are very rare, for the same reason that æalogists are rare: because few people have the chance to explore multiple worlds and study the life therein. In practice, therefore, most etorists know well only the life on their own world. This means, of course, that etorists may be completely unaware of, or at least unfamiliar with, entire empires or universes that don't exist on their own worlds. In particular, for instance, there will generally be no phasmologists on a nonmagical world.
Creation and reproduction
There are six main ways that new life forms can be created: by replication, by artificial creation, by ananome, by transformation, by procreation, or by spontaneous generation. There may be some overlap between these methods; a being that transformed other life forms into entities completely identical to itself would, for instance, be reproducing simultaneously by replication and transformation. Nor do these six methods necessarily exhaust all possible means of creating a living entity; there may be a few unusual instances that don't quite fit any of these cases.
Certain taxa are characterized by their means of creation, among other factors. Organisms generally reproduce through procreation (or occasionally through replication); machillas generally are created artificially. When another life form is involved in the creation process (that is, in all cases but spontaneous generation and some cases of artificial creation), the original life form is called the parent, and the new entity the child. It is, of course, entirely possible for the creation of a new life form to involve more than one parent; indeed, in procreation, in particular, this must be the case by definition.
Perhaps the conceptually simplest process, replication occurs when one parent life form gives rise to an identical being, or at least a being which has the potential to become identical to the parent. In the case of life forms with some form of genetic material, the parent and child have identical genes.
Replication can occur through a number of different means. The parent can merely split into two similar children (binary fission); it can grow a smaller copy of itself that may later break away (budding); or a parent divided into multiple discrete parts may grow a new copy from each part (fragmentation). In some cases, life forms that normally reproduce through procreation may instead reproduce through replication under certain conditions, a phenomenon known as parthenogenesis.
Artificial creation describes a process in which one or more parent life forms instill life in some formerly nonliving object or construction external to themselves. This may mean building a mechanism sufficiently complex to achieve life technologically, or it may mean placing a magical enchantment upon an object to bring it to life. The vivification process need not be done intentionally or consciously, and in fact the parents need not be aware that they are doing it. It is entirely possible for some utterly alogous life form to have the power to animate nonliving matter, and to therefore, without any comprehension of what it is doing, to be engaged in the artificial creation of other life forms.
Ananome is a process in which one or more parent life forms reshape and redistribute their substance to form one or more child entities different from the parents. If there is only one parent but several children, the process is known as darsis; if several parents but only one child, the process is known as henosis. Technically, several forms of replication could be considered instances of darsis, and the joining of gametes in some versions of procreation could be considered henosis, but ananome can also produce new life forms in many other ways. There are, in fact, some life forms that reproduce exclusively through ananome, such as the nelder of Tamamna, which each form through the henosis of three other organisms; and the sanhvin of Loge, which arise through the darsis of a larger parent organism.
Sometimes a new life form may be created by the transformation of an existing life form. To what extent the new life form really qualifies as new is a subjective matter; when a caterpillar changes into a butterfly, its form becomes drastically different, but it is still generally considered to be the same entity (and certainly to still pertain to the same species). Even a human is altered quite a bit as it grows from an embryo to an adult, but without usually being thought of as actually becoming a different life form altogether. Still, while the matter is largely moot, there are some transformations sufficient to convert a life form into a different being entirely. Generally this applies when the transformation does not occur to all members of the species, when it comes from some external source, and when the transformation is mental as well as physical. Some forms of undeath form an example of such a transformation.
Procreation is a process by which two or more parent life forms combine their genes and create one or more children with a genome that is some mixture or combination of that of the parents. This isn't to say that the child will necessarily look like the parents; though they have the same genetic structure, the genes may be expressed sufficiently differently to make the parent and child dramatically dissimilar. Indeed, it's not particularly uncommon for the child to look very different from the parents, but similar to the parents' parents, a phenomenon called alternation of generations.
In some circumstances, in some cosmoi, living beings can spontaneously appear from nonliving material. This may be because of ambient magic, or it may be because of some more fundamental physical or chemical phenomenon. Arguably, on any world where life didn't arrive from elsewhere (and wasn't somehow always present), spontaneous generation had to happen at least once to create life in the first place, but in that case when it happened depends on how one defines the onset of life, and it makes more sense to consider life to have arisen gradually and not at a specific point.
- Life form on Wikipedia