By Claudine Ryan

Apples, oranges and pears are fruit. Broccoli, carrots and cauliflower are vegetables. Simple, right?

But it is not always that straightforward. For instance, not all of these items – mandarin, kiwifruit, fig persimmon and rhubarb – are fruit (and you’ll have to read on if you want to know which one isn’t).

There are also plenty of fruit that you count in your veg tally for the day. (Experts recommend you eat five serves of veg a day and two of fruit).

From a botanical perspective there is quite a clear definition of the difference between the two, says Pauline Ladiges, a professorial fellow at the University of Melbourne’s school of botany.

Fruit, she says, are the ovaries of a seed-bearing plant that develop after fertilisation. Quite simply, if it has seeds it is a fruit.

“The ovary is the female part of the flower and after pollination (or fertilisation) the seeds develop protected inside the ovary, which swells and ripens. Fruits are often fleshy, coloured and sweet when ripened to attract animals to disperse the seeds,” Ms Ladiges says.

“Some fruits are dry or even woody in the case of eucalypts – these are called capsules rather than gum ‘nut’ (it is not a nut) – or banksia and macadamias, their fruits are called follicles.”

By this definition not only are apples, oranges and pears considered fruit, so too are tomatoes, olives and cucumbers. But that is not all. Legumes are also… you guessed it, fruit.

“Think of a pea pod. The whole thing is the fruit and the peas that you eat are in effect the seeds. Legumes are a type of fruit,” Ms Ladiges says.

So if all of these foods are fruit, what exactly are vegetables?

“Vegetables, strictly speaking from a botanical point of view, are the non-flowering bits. So the leaves, we eat spinach leaves. The stems, we eat celery. We eat roots, like carrots and turnips. We eat the tubers like potatoes,” Ms Ladiges says.

This all makes perfect sense, except we’ve been led to believe that fruit are sweet and vegetables are savoury.

Take tomatoes, for instance. When was the last time you made a tomato cake? While botanically these are fruit, most of us use them in savoury dishes – soups, pasta sauces, salads or stews.

“A tomato is definitely a fruit, but because it is savoury some people might call it a vegetable. Strictly speaking it’s not, it’s a fruit,” Ms Ladiges says.

“There’s a grey area where some things, like peas and pumpkins, being fruits but we treat them as vegetables.”

Some vegetables that are fruit still count as veg

This would all be an academic argument except we are told that we need to eat five serves of vegetables a day, and only two serves of fruit.

Fortunately, the Australian Dietary Guidelines take the more ‘culinary’ approach. So even though there are a bunch of vegetables that are technically fruit, they still count as part of our daily vegetable intake (which is good thing, because even with the expanded vegetable definition only six per cent of us are getting what we should).

Professor Amanda Lee from the School of Exercise and Nutrition Science at Queensland University of Technology says this is partly because the dietary guidelines are based on scientific research.

“Most relevant health studies, but not all, tend to use ‘functional’ categories rather than botanical categories of fruit and vegetables, because that’s how those taking part in studies use these foods,” says Professor Lee, who was the chair of dietary guidelines working committee.

She also points out there is less difference between the recommended amounts of fruits and vegetables than we might think.

“One standard (convenience) serve of veggies is 75 grams and one standard (convenience) serve of fruit is 150 grams… These reflect the optimum quantity of intake of those foods associated with positive health outcomes overall,” she says.

Many of those foods that fall into the functional ‘vegetable’ group tend to be slightly less energy-dense, that is lower in kilojoules than ‘fruit’. This is why we’re encouraged to eat more of them than fruit (or any other food).

But the bottom line is most of us are eating nowhere near enough fruit or vegetables, regardless of whether you’re talking about botanical or culinary definitions. So feel free to eat up when it comes to tomatoes, pumpkins, zucchinis, corn, cucumber, peas and beans. And while you’re at it, be sure to enjoy apples, pears and oranges.

Did you know all of this? Did anything surprise you?

This post originally appeared on ABC News.

© 2015 Australian Broadcasting Corporation. All rights reserved. Read the ABC Disclaimer here.