Definition: A composite material consisting largely of calcium phosphate and collagen and making up the skeleton of most vertebrates.

Alright class, settle down, let’s take a look! That's a very precise definition from the dictionary, isn’t it? Let’s break it down nice and slow. “Bones,” you see, are much more than just hard bits we can poke! Let’s start with “composite material” – that means they're made of many different things working together. Think of it like a recipe - lots of ingredients combine to make something special. Now, "calcium phosphate" – this is the main ingredient, a big part of what makes them strong and white! It’s like the building blocks, giving bones their solidity and structure. Calcium gives them that “hard” feeling, you know? And then we have “collagen” , which is a protein - it's kind of like the glue holding everything together. It’s flexible and stretchy, allowing your bones to bend and move with ease! Finally, "skeleton of most vertebrates" – that means most animals with backbones (fish, birds, mammals like us!) have these amazing structures inside them supporting their bodies. They're the framework that keeps us upright and moving around! So, in short, bones are a complex combination of hard minerals and stretchy protein, forming a protective and supportive structure for our bodies. Do you all have any questions about what we’ve covered today? Don’t be shy – let's explore this further together!