I have put together this glossary from various sources; which includes the books mentioned below, internet, and research papers. The glossary has terms related to growth habits, growth types, habitats etc.

• Aerial: Exposed to the air, like the aerial roots or the orchids.
• Ageotropic: Growing in the direction opposite to gravity.
• Allopatric: Orchids growing in different regions.
• Ascending: Climbing upwards.
• Autotrophic: Orchids having chlorophyll (green pigment) and capable of making their own food from inorganic subatances.
• Caespitose: Forming tufts or clumps; usually used for epiphytes.
• Deciduous: Plants which shed their leaves after an active growing season.
• Endemic: Confined to one particular region.
• Epigeal: Growing on or close the soil surface.
• Epilithic: Orchids growing on rock surfaces.
• Epiphyte/epiphytic: A plant which usually grows above ground, on trees, wires, poles etc. and are not parasitic. Nutrients are derived from from rain, air and available debris.
• Evergreen: Orchids which do not shed their leaves and are green throughout the year.
• Geophyte: Terrestrial orchids which are capable of surviving in arid conditions.
• Gregarious: Orchids growing is groups.
• Habit: Life form of an orchid; its physical appearance.
• Habitat: Environment in which an orchid grows.
• Hemiparasitic: Having partially autotrophic as well as parasitic mode of nutrition.
• Herbaceous: Orchids whose above ground shoots survive for only one season.
• Heterotrophic: Orchids which do not have chlorophyll (the green pigment), so are unable to synthesis their food and depend on either decaying organic material or on some kind of symbiotic relationship.
• Holomycotrophic: Deriving nutrition from symbiotic fungus.
• Indigenous: Belonging to a particular region.
• Lithophye/lithophytictic: Orchids which grow on rocks.
• Littoral: Growing near the coastal regions.
• Monocot: A group of plants which have a single cotyledon in the seeds; Orchidaceae belong to this group.
• Monopodial: having a single main axis which grows continuously, from which leaves and flowers arise
• Monotypic: a genus made up of single species.
• Mycoheterotrophic: Leafless orchids which live in associations with fungi and derive nutrition from the fungi.
• Mycorrhiza: A fungi which exists in symbiotic relation within the orchid roots.
• Myrmecophyte: Orchid having association with colony of ants.
• Pendulous: Drooping.
• Phorophyte: Trees or plants which act as host for epiphytic orchids
• Procumbent: Trailing over the ground without rooting.
• Rupicolous: Orchid growing among rocks.
• Saprophyte/saprophytic: Leafless plant which derives its nutrition from dead organic matter.
• Saxicolous: Found growing on/among rocks.
• Scandent: Having a climbing habit.
• Semiterrestrial: Orchid being able to grow as a terrestrial as well as an epiphyte.
• Symbiont: One of the individual involved in the symbiotic relationship.
• Symbiosis: Mutually beneficial relationship between two different types of organisms.
• Sympodial: when the main stem has limited growth and gets branched a number of times.
• Synanthous: Producing pseudobulbs, leaves and apical inflorescence together.
• Temperate: Moderate climate without having extreme temperatures.
• Terrestrial: Orchids growing on ground.
• Tropical: found in tropics; having hot weather.
• Xerophyte/xerophytic: Plants found growing in arid or dry conditions.

Main Sources

1. H. J Chowdhery. Orchid flora of Arunachal Pradesh.
2. Dressler, Robert L. Phylogeny and Classification of the Orchid Family