Botanical names have the distinct advantage of referring to one and only one plant, with certain exceptions.  The use of these names makes communication between widely scattered gardeners and plants-men more precise.  Since the internet has made the world smaller, it is important that we all refer to the same plant by the same name if our discussions are to have any meaning.  If you point out a mint plant to a fellow gardener, there is understanding. If you ask me why your mint plants have little holes in them, I can surmise that snails are eating them, but I have no idea what plant you are growing since there are many genera of mints.

Genera is the plural of genus, and genus is one of the components of a plant name. The binomial (two name) system of naming all organisms on the planet groups them into various kingdoms, divisions, orders, families, and genera.  So, the genus is the basic grouping of similarity or relationship between organisms.  It is at this level that we want to be more specific, and that is done by adding another word called the "specific epithet." The combination of genus and specific epithet into a single phrase called the "species" is the basic component of botanical nomenclature.  There are finer divisions such as cultivars, variety, and subspecies describing minor variations, but "species" is the level at which gardeners and plants-men operate.

Genus:

Genus is the name given to a group of organisms whose physical characteristics are permanent, similar, and largely confined to that group.  In Latin, it is a naming noun derived in part from medieval Latin, classical Latin, and Latinized versions of words in other languages, principally Greek.  This is why these words may often seem foreign to you.

Solanum, for example, is a Latin word for a group of plants including herbs, shrubs, trees, and vines.  There are 1400 species in this group and all of the plants in this group are slightly to heavily toxic, “clammy” or hairy plants with star or bell-shaped flowers with five lobes whose fruit is always a berry.

At the other extreme, is the genus Nicandra consisting of a single species.  It is not a Solanum because it shares only the flower structure, but none of the other characteristics. Nicandra shares characteristics with other genera, like Physalis, but is otherwise unique, and thus deserving of its own name.  By the way, Nicandra was named after the Greek botanist, Nikander of Colophon (c. 150AD).

Thus, you can see that a genus may get its name in honor of a person or it may get its name from its origins, i.e. what natives called it where it was discovered.  Typically, the name comes from one or more of the most prominent characteristics that define the group.  Helipterum, for example, comes from the Greek (helios=sun) and (pteron=wing). Because the 26 letters of the English language are so confining a number of generic names are simple anagrams of existing genera yielding names such as Sibara, Norysca, Ubochea, and Zacateza.  A few are anagrams of geographic places such as Lobivia and Jacaima.

Now you should be able to recognize that Genus, for all practical purposes, is just a name and may well be subject to change.  For example, Chrysanthemum members were recently split off to join other groups, such as Dendranthema, Leucanthemum, and Tanacetum. Those that went to Dendranthema are now on their way back to Chrysanthemum.

Taxonomy is the scientific study of the proper classification of organisms so that there will be no confusion.  But because many botanic systematists are making contributions to this field, a single species could be moved from one family to another, or even to a different order in a matter of years.  For example, because of philosophical beliefs, some botanists would prefer that the common tomato (Lycopersicon esculentum) be renamed  -- Solanum Lycopersicum. Because of this, suggestions for renaming a plant, and the reasons for it must be decided upon by a committee before the change can be agreed upon. One committee decides what goes on the agenda while another will investigate the proposed change. Finally another will interpret the International Rules of Botanical Nomenclature for consistency.  The main committee will then split into cliques and coalitions that will decide the final appellation of the plant.

A genus is a group of plants sharing a unique set of common characteristics that have been given the same first name.  

Specific epithet

The second word in the botanical binomial is the specific epithet.  It has meaning or it has no meaning of its own, subject to the same lack of rules, abundance of rules, and avoidance of rules as found above.  For every specific epithet that has a meaning in its archaic Latinized history, there is another which has been invented playfully or otherwise, and which has no meaning whatever.

The specific epithet, when added to the genus to form the binomial, now becomes the species, and this is what sets one plant apart from another within the genus.

A specific epithet may be a noun or an adjective.

It may indicate a distinguishing characteristic of structure or flower color in the species. Elatus, for example, is an adjective meaning tall.

It may indicate something about the habitat where a species happens to flourish. Palustris, for example, is an adjective meaning from swampy places.

It may indicate the location where the species was first discovered. Monspeliensis, for example, means from Montpelier.

It may honor a person. Davisii, for example, means Mr. Davis

There are thousands of specific epithets.  Some are used only once, and never applied to any other plant. Some are used across many different genera. Some have prefixes, suffixes, and different endings depending upon other criteria. 

Some specific epithets have an historic meaning while others were just given a name.

Prefixes are numerous both in the Latin and the Greek languages. Atro, for example, is a qualifying word meaning "dark", as in atropurpureus.  The prefix changes the meaning from purple to dark purple.  Intra and endo, for example, are the Latin and Greek prefixes, respectively, meaning "within". New epithets are invented from time to time, and their meanings require a little guessing if you cannot find them in the references.  Monarda austromontana, for example, leads one to believe that this Monarda is native to (australis=south, southern) plus (montana=from the mountains), therefore "from the mountains to the south."  This plant does indeed come from the mountains of Southwestern USA, notably from the States of New Mexico and Arizona.

Suffixes permit a wide variety of words to be formed from a single word.  Ulentus is a Latin suffix meaning "abundance", as in succulentus, "full of juice".  Oides is a Greek suffix meaning "resembles", as in Boltonia asteroides, "like an aster". It does help to know the meaning of the most common prefixes and suffixes because they will help you to understand the meaning of many specific epithets without the need to look them up.

Because nouns in Latin change form to express relations or different genders, its following descriptive adjective may or may not reflect the gender and the declension of the noun it describes.  For example:

Tricolor and leptorhiza are examples of adjectives without endings to reflect the noun's gender.

Annuus, annua, and annuum all have exactly the same meaning, which reflect the gender of nouns. But the ending is different depending upon the gender of the genus name, i.e., masculine=(us), feminine=(a), or neutral=(um).

Humilis (humile), mirabilis (mirabile), Minor (minus) and major (majus) are examples of adjectival endings that follow no convention whatsoever.

If by now you are totally confused, do not worry too much about the issue.  Instead just follow this advice:

Forget the Latin. Treat all botanical binomials as English words.  Simply add these words to your vocabulary as you have occasion to use them and relate the specific binomial to the plant.

Forget the adjectival endings as they tend to be anomalies.  The meanings of the stems of these words will remain constant across all genera.

Simply remember that every botanical binomial refers to one and only one plant, and that no definition of the names used is either required or useful.  Adopt these word combinations into your language and realize that other plants-men will understand what you mean. Understand that a synonym is an obsolete name that has been officially discarded.

Do not do business with a seller of seeds or plants that does not provide you with the botanical name of the plant.  If they don't know what they are selling how are you supposed to know what you are growing?  You cannot ask a question about a plant if you cannot say what it is.  Guesses about unknown plants and seeds always result in bad advice.

In summary, the language of common names of plants is a foreign language. Some common names refer to as many as 12 different species across many different genera.  Some species have as many as 12 different common names. Those nicknames have no real meaning because they each have too many meanings to be useful.  Botanical names, on the other hand, have no real meaning, however, each of them refers to one and only one plant.  That fact makes them invaluable to you.  Using botanical names will save you much time and grief later on.

Dictionary of specific epithets:

The following is a listing of the most common epithets referring to plant or flower structure, color, or environment where found.  Not included are epithets referring to a place because there are over 700 of those.  Also not included are epithets honoring a person as they too, number in the hundreds.  The dictionary is alphabetic.