Ask A Scientist General Science Archive

name        Julian
status       student
grade        4-5
location     N/A

Question -   What is the difference between a vegetable and a
grain?  Why is rice a grain but a lentil is a vegetable?
---------------------------------------
Grains are specifically the seeds from different types of grasses.   Find
some pictures of wheat, rice, oats, and even corn plants, and you'll notice
they look similar to the grass that grows tall in unmowed fields.  The word
"vegetable" does not have such a precise meaning, but it usually refers to
non-sweet tasting edible plant parts.  Many things that are called
"vegetables" are actually fruits (the ripened ovary of a plant) such as
tomatoes and squash.  However, grass seeds are usually called "grains" not
"vegetables" (although some people call corn a vegetable and some people
call it a grain).

Aurora Toennisson

Dept. of Entomology and Plant Pathology
University of Tennessee
====================================================================
The word "vegetable" means many different things, depending on context.
To a grocer, some plant-based foods are classified as vegetables, others
as fruits, others as grains, etc.  Mostly, this traditional
classification has to do with how the foods are used in cooking.
However, the grocer's distinctions have almost nothing to do with plant
biology.  To a botanist, there are much more exact definitions.  For
example, a "fruit" is the mature ovary of a flowering plant, and despite
the fact that we tend to consider peas and beans to be vegetables, there
is no question that they are, botanically speaking, fruits.
Incidentally, the word "vegetable" actually is not used scientifically
and it has no clear-cut definition.
A "grain" (technically called a caryopsis) is the fruit of members of
the grass family (Poaceae, aka Gramineae).  The grasses are by far the
most important food plants for humans; they include corn, wheat, rice,
barley, oats, etc.  All grains are grasses.
Probably the second most important food plant family is the legume
family (Fabaceae, aka Gramineae).  This family includes peas, beans,
soybeans, chickpeas, and - you guessed it - lentils.  Foods from the
legume family are sometimes called "pulses".
In summary, grains are grasses; lentils happen to be in a different
family, the legumes.  In my opinion, both could be considered
vegetables, but different people will use the word vegetable
differently.

C. Perkins
====================================================================