A complete flower has flower parts arranged in four concentric circles around a floral axis.  Each circle (known as a whorl) has a set number of parts for a species. The outer two, non-reproductive whorls are called the perianth. The two inner whorls are the reproductive parts. The photo shows a section through the flower of a Wild Cherry. Note that incomplete flowers have one or more of the flower parts missing. To learn more about these flowers click HERE. From the outside towards the centre the flower parts are:-


Narcissus flower parts
1. The sepals, collectively known as the calyx (Greek for husk or pod) protect the flower parts as the flower bud develops. Most sepals are green but in some flowers the sepals and petals are identical and both are called tepals (as in most Monocots) 

2. The petals, collectively known as the corolla, attract pollinators and provide landing sites for them. 

3. The stamens (male Androecium) – each one consists of a filament supporting an anther which produces and releases pollen grains.

4. The carpels (female Gynoecium) – each one consists of an ovary with ovules, a style and a stigma on which pollen grains are received. The ovary becomes a fruit and the ovules become seeds. A flower may have one or more carpels.

Botanists use a Floral Formula as a shorthand way of describing a species – see below
Floral Formula of the Wild Cherry shown in the photo above. This species has 5 sepals, 5 petals, 20 stamens (filaments + anthers) and 1 carpel (ovary +1 style/stigma). Its floral formula is K5 C5 A 20 G 1. 

This simplified floral diagram shows a flower with only 5 stamens and formula K5 C5 A5 G1.