A compound fruit is one that develops from several ovaries

Ovary (plants)

In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...

 in either a single flower

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

 or multiple flowers. In contrast, a simple fruit develops from one ovary.

• Compound fruits may be aggregate fruits, in which one flower contains several ovaries, each of which develops into a small fruit. These small fruits are joined tightly together to make a larger fruit. An example of this is a raspberry
  Raspberry
  The raspberry or hindberry is the edible fruit of a multitude of plant species in the genus Rubus, most of which are in the subgenus Idaeobatus; the name also applies to these plants themselves...
  
  . Each fleshy lobe in a raspberry is actually an individual fruit, but they are joined at their bases. Despite having the suffix "berry
  Berry
  The botanical definition of a berry is a fleshy fruit produced from a single ovary. Grapes are an example. The berry is the most common type of fleshy fruit in which the entire ovary wall ripens into an edible pericarp. They may have one or more carpels with a thin covering and fleshy interiors....
  
  ," aggregates cannot be berries, which are composed of a single ovary.
• Compound fruits may also be multiple fruit
  Multiple fruit
  Multiple fruits are fruits that are formed from a cluster of flowers . Each flower in the inflorescence produces a fruit, but these mature into a single mass...
  
  s, in which several flowers, each with an ovary, develop into small fruits that are clustered or fused together into a larger fruit. An example of this is a pineapple
  Pineapple
  Pineapple is the common name for a tropical plant and its edible fruit, which is actually a multiple fruit consisting of coalesced berries. It was given the name pineapple due to its resemblance to a pine cone. The pineapple is by far the most economically important plant in the Bromeliaceae...
  
  . Each section of a pineapple was an individual fruit from an individual flower, but they have fused to form the pineapple. Another example is the fig
  Ficus
  Ficus is a genus of about 850 species of woody trees, shrubs, vines, epiphytes, and hemiepiphyte in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone. The Common Fig Ficus is a genus of...
  
  .

Grape

Grape

A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...

s grow in clusters, but are not compound fruits. Each grape is grown from one ovary in one flower, and each grape remains an independent fruit. an aggregate fruit or etaerio is a group of simple fruitlets that develop from the free ovaries of a single flower.

A List of Compound Fruits

• Raspberry
  Raspberry
  The raspberry or hindberry is the edible fruit of a multitude of plant species in the genus Rubus, most of which are in the subgenus Idaeobatus; the name also applies to these plants themselves...
  
  
• Pineapples
• Dewberry
  Dewberry
  The dewberries are a group of species in the genus Rubus, section Rubus, closely related to the blackberries. They are small trailing brambles with berries reminiscent of the raspberry, but are usually purple to black instead of red.Dewberries are common throughout most of the Northern Hemisphere,...
  
   and Blackberry
  Blackberry
  The blackberry is an edible fruit produced by any of several species in the Rubus genus of the Rosaceae family. The fruit is not a true berry; botanically it is termed an aggregate fruit, composed of small drupelets. The plants typically have biennial canes and perennial roots. Blackberries and...