Flowers may be single (referred to as a FLOWER) or in clusters or groups (referred to as an INFLORESCENCE)

Flower Parts: FIG
Bract - a reduced leaf-like structure that is located at the base of the flower / inflorescence
Calyx - the sepals of a flower, the outer portion of the perianth
Corolla - petals of the flower, the inner portion of the perianth
Disk - the center part of the head with small, tubular or disk shaped flowers
Involucel - smaller, minor involucre
Involucre / Involucral Bracts - whorled bracts may be at the base of a single flower or inflorescence
Pedicel - stalk of a single flower that is in an inflorescence (group of flowers)
Peduncle - stalk of an inflorescence or a single flower
Perianth - calyx and corolla together, both parts often similar in appearance
Petal - portion of the corolla, may be fused or in groups
Pistil - refers to female reproductive organ of a flower, made up of the stigma, style and ovary
Ray - may refer to the tongue shaped part of a ligulate flower or umbel branch
Sepal - leaf that subtends the calyx
Stamen - refers to male reproductive organ of flower, made up of the filament and anther
Stigma - end portion of a pistil where pollen is received
Style - stalk-like portion of the pistil that connects the ovary and the pistil
Ovary - bottom portion of the pistil that becomes the fruit
Spur - sac organ attached to petal, sepal, calyx, or corolla
Stipe - supporting stalk for the ovary in some flowers
Tepal - sepals and petals that are fused and indistinguishable from one another, seen in Juncaceae

Flower Terms:
Appressed - flattened up against another structure
5-merous - arranged in five parts, or in sets and/or multiples of 5
Ovate - egg-shaped with the broadest portion at the bottom
Pedicillate - having a pedicel (compare to sessile)
Pistillate - without a stamen but having a pistil
Rosette - a radial cluster of flowers arranged around stem and/or leaf axil
Sessile - attached directly the stem, lacking a pedicel
Staminate - flower has only male flower parts (stamens)
3-merous - arranged in three parts, or in sets and/or multiples of 3
Unisexual - flower has only female or only male parts
Whorled - flowers arranged around a central axis (generally stem or peduncle)
Terminal - flower or inflorescence located at the end of the stem
 

Flower Types:
Actinomorphic - radially symmetrical
Bilabiate - 2-lipped imperfect flower
Composite - having ray and disk flowers (or another two flower types) on the same flower
Dioecious - male or female flowers are on separate plants
Imperfect - has either male or female flower parts each flower
Perfect - having male and female reproductive organs in each flower
Salverform - flower has slender base which open at the top
Spadix - often found with the spathe, a spike that has small flowers
Spathe - greatly enlarged bract which surrounds and inflorescence (often encircles it)
Tubular - shaped like a cylinder or tube
Urn-shaped - shaped like a pitcher, round with a narrow, tapering top
Whorled - flowers arranged in a ring around a stem
Zygomorphic - bilaterally symmetrical

Inflorescence Types:
Catkins - hanging inflorescence made up of spikes or racemes
Compound Umbel - similar to an umbel but with a second branch point from each pedicel
Inflorescence - refers to a flower grouping
Panicle - same as the raceme but branched
Raceme - long flower cluster (inflorescence), has pedicillate flowers, unbranched
Spike - unbranched inflorescence with sessile flowers
Umbel - inflorescence that has numerous pedicel arising from a common point