Erica's Original Notes Fruit means something different to a botanist than to a green grocer.
Fruit may have: a) one seed (acorn); b) many seeds (pea, bean); or c) several fruitlets grouped in one head (buttercup).
Fruit may be: a) fleshy (tomato); b) drupe (stone fruit - apricot) or c) pome (apple).
Pineapple is a swollen stem holding fruitlets.
Apple and pear are really the swollen end of the stem.
Nuts are themselves seeds.
False fruits are blackberry, fig and strawberry.
Summer fruit, such as blueberry and Amelanchier, are high in sugar for songbirds.
Fall fruit, such as dogwood, are high in fatty compounds for migratory birds.
Winter fruit, such as sumac and viburnum, are high in carbohydrates for resident birds.
NOTES Updated 2013 (RP): Erica’s notes on this topic are very brief. To botanists, beans and tomatoes are fruits! If you would like to see the large variety of fruits that she alludes to a good starting point with good illustrations is The Cambridge Illustrated Glossary of Botanical Terms (2000) by Michael Hickey and Clive King. (This is a reference book in the garden library.)