I am Just confused whether solitary means single flower in the whole plant or one flower on one branch of the plant?
Solitary flower means one flower at a specific position of a plant. It usually accompanies with another word either terminal or axillary.
Soliary terminal means a flower present at the apex of the main stem or its branches. e.g. Trillium grandiflorum.
Image taken from http://ohioplants.org/inflorescences/
Solitary axillary means a flower arising from the axil of a leaf. e.g. China rose.
Image taken from https://commons.wikimedia.org/wiki/File:China_rose.JPG
No. It doesn't mean that a plant has a single flower.It speaks all about the position of the flower. Think of roses , they are solitary terminals and are in numbers in each plant, always growing at the apices of branches.
Source: My two years of learning Botany as an additional Undergraduate subject.
Solitary flower could be single or many flowers in a branch. How many flower is in a 'branch', That is not the concept of solitary flower. The concept is about 'how many flower is there in an inflorescence (branches specialized for flowers)'
Solitary flower a flower NOT in a "inflorescence" (Cluster of many flowers together). Or in another sense, Solitary flower is an inflorescence made up of only 1 flower.
The complete terminology is: "inflorescence with solitary flower".
To understand what is an inflorescence with solitary flower, you need to look for what is NOT an inflorescence with solitary flower.
User @SanjuktaGhosh gave beautiful examples of solitary flowers, so I gave example of only what is not that.
Brassica inflorescence (Raceme, which is racemose).
Foeniculum sp inflorescence (compound umbel, which is cymose)
We can see now, 'inflorescence' means specialized stem axis/ branches, containing mainly flowers (and some bract leaves). In nature, flowers usually occur in such specialized stems, and look like 'cluster' (many flowers together)
But what if a flower occur NOT in such cluster? rather solitary, at clear distance, and the axis on which flower borne, is not distinctive from the rest plant-body?
We couldn't see any 'inflorescence'; however it is considered as an inflorescence with only 1 flower, and from growth-pattern it is a subset of cymose-inflorescence (since the only-bud is the top-bud of the stem going to be flower)
what we've been taught
College Botany/ VOL-1/ Gangulee, Das, Datta/ New Central Book Agency