When I first started studying Botany  in 1995 at the University of Utah (with real teachers! not just winging it with my little wildflower guide that Santa/my mother left in my stocking when I was eleven), it was really helpful to understand Latin (and often Greek) root words to get a hint when identifying a plant, or knowing what it was useful for, or sometimes even what kind of habitat it likes. Plant names are codes imbued with meaning.

Some names, like Theobroma cacao, (chocolate) are just perfect. Theos means “god” and bromus is “food” in Greek. And Liriodendron tulipfera is translated basically as “tulip-flowered Lily-tree.”

Here is a small selection of basic root words that are commonly used in herb nomenclature – some are pretty self-evident, others a revelation.

Descriptions of the plant: (first few examples are root words combined with other root words)

• -atum: of the flower, for example:
  • variegatum : variegated flowers
  • paniculatum : with flowers in panicles
• -flora : of the flower
• -folium : of the leaf
• -phylla : of the leaf
• acro : toward the top
• capillus : hair
• caudatum : with a tail
• dioeca : two houses (describing separate male and female parts)
• formosum : beautiful
• hispidulum : finely bristly
• mollis, villosa : softly hairy 
• ciliaris : fringed with hairs
• fistulosum : hollow-stemmed
• sativum : edible
• striata : striped
• vera : true (ex. Aloe vera)
• triphylla, trifolium : three-leaved
• officinalis : sold as an herb
• glabra : smooth
• arctos : a bear
• acetosa : acid-leaf (Rumex acetosa or Sorrel, which has a lemon-tasting leaf)
• phytolacca : plant with red dye (lacca after Crimson Lake, a type of dye)
• maculatum : spotted
• officinalis : medicinal use, sold in the apothecary
• annuum : annual
• perennis : perennial
• vulgaris/vulgare : common

Habit

• arvensis : of cultivated fields
• pratense, pratensis : of a meadow
• reptans, repens : creeping (ex. Ajuga reptans)
• tenella : dainty
• calustrus : in a wet meadow
• hortensis : garden origin; cultivated for many years, not known from wild

Shapes

• spicata and stachys : spike
• stivum : cultivated
• tuberosum : tuberous
• capitatus : in a dense head
• macro : large
  • macrorrhiza : with a large root
  • macrophylla : large leaf
• cordata, cordate: heart-shaped
• uniflora : single flower
• helianthus : sun flower
• hederacea : like hedera (ivy)
• biloba : two lobes

Origin

• virginiana : of Virginia (North American origin)
• occidentalis : western
• canadensis : first seen in Canada
• borealis : northern woods

Colors

• rubra : red
• rosea : rose-colored
• flavum : yellow
• incana : grey
• cuprea : coppery
• tricolor : three color
• caerulea : blue
• versicolor : one color blending into another

Some more

• clary : clear (as in Clary sage, used for hormonal issues, usually means lymph needs clearing; also for eyes)
• leon- : lion (as in Leonorus cardiaca or Motherwort)
• Hippo- : horse (as in Aesulus hippocastanum or Horse Chestnut
• agan : very much and stachys : a spike, work together to make up ‘Agastache‘ which refers to this Giant Hyssop’s numerous flower spikes.
• Allium schoenoprasum: schoinos which refers to a rush and prasum, a leek, referring to the rush-like leaves of chives.

And a few names with Greek origin:

• Althaea – althaine is ‘to heal’, refers to medicinal properties
• Amaranthus – amarantos is ‘unfading’, refers to long-lasting flowers
• Chamaemelum – chamai is ‘on the ground’ and melon is ‘apple’, refers to apple-like scent and low habit
• Chelidonium majus : chelidon is ‘swallow’ in Greek, refers to the timing of when the plant flowers, as the swallow arrives. And majus is ‘larger’.
• Glycyrrhiza – glykis is ‘sweet’, refers to sweet taste of the root (rhiza is also Greek)
• pyrethrum – pyr is ‘fire’, refers to use as rubifacient

I recommend Timber Press’s Dictionary of Plant Names for further reading – it is not specific to herbs, and is not organized by root word but by Genus name, which sometimes isn’t that helpful because many Genus names are just given names, with no ‘meaning’ other than the name of that group of plants… but there is still a lot of good information.