The following list of terms and definitions are commonly used when referring to non-native plant species.
1. Non–native: not naturally occurring in a given area; nativity (origin) is from a different geographic location.
2. Waif: occasionally encountered in the flora on a more or less regular basis, but not established and probably not capable of permanent establishment; generally present because of the direct assistance of people. Some Arkansas examples would be the garden onion (Allium cepa) and corn (Zea mays).
3. Adventive: occasionally encountered in the flora, generally with the direct assistance of people, for example, marijuana (Cannabis sativa) plants found growing along roadsides or alleyways are often present in these areas because of seeds that people have deposited in those areas.
4. Spontaneous: occurring in the flora without the direct assistance of people, but not firmly established as part of the flora. Spontaneous plants are present from sexual or asexual reproduction, not being intentionally planted or deposited by people or their activities (plants are present via natural causes).
5. Escaped: similar to spontaneous; generally the individuals originate from a source pool of cultivated plants.
6. Established: successfully reproducing and maintaining a stable population size in the flora.
7. Naturalized: established in a given area as though the species had always occurred in the flora.
8. Invasive: species moves into habitats where it previously did not occur, altering them, and often displaces the native species therein. The photograph at the top right shows numerous, spontaneous, juvenile plants of glossy privet, Ligustrum lucidum in a disturbed, semi-wooded area on the HSU campus. There are literally dozens of additional spontaneous L. lucidum plants in the immediate vicinity that are not pictured below; this type of reproductive success is not uncommon for glossy privet in certain areas of Arkansas. The seeds of L. lucidum are bird-dispersed, as are those of many of the most invasive woody plant species. The bottom photograph shows spontaneous juveniles of mimosa, Albizia julibrissin (left) and Chinaberry, Melia azedarach (right); both of which are at least somewhat invasive in Arkansas, in particular, M. azedarach.