You were told the commutative, associative and distributive laws in a single breath, and they blurred into one vague phrase: "you can rearrange stuff." But they do three very different things. Commutativity swaps two items. Associativity regroups the brackets. Distributivity spreads one factor across a sum. This satellite gives you one clean picture for each — so that when you use them in algebra, you know which rearrangement you actually performed.
Commutative — swap the two inputs
Take two boxes holding a and b apples. Put box a on the left and box b on the right. Total apples: a + b. Now physically swap the boxes so that b is on the left and a on the right. Total apples: b + a. Same apples, same total.
Multiplication of real numbers works the same way: 3 \times 4 is three groups of four, 4 \times 3 is four groups of three, and a 3 \times 4 rectangular grid is the same grid whether you count rows first or columns first. Why: the grid has 12 dots no matter which direction you scan.
Associative — regroup the brackets
Now take three boxes a, b, c. The commutative law lets you swap two of them; the associative law lets you change which pair you add first. Either (a + b) + c — add the first two, then add the third — or a + (b + c) — hold onto the first, add the other two first, then combine. Same total.
Associativity and commutativity are independent: swapping the boxes is one kind of freedom, rebracketing them is another. The fact that addition enjoys both is what lets you write 3 + 5 + 7 + 2 with no brackets and no worry about the order — any rearrangement lands on the same total.
Distributive — spread one over two
Now the new shape. You have one factor a and a pair of things, b and c, that have been added together. Distributivity says you can multiply a into the bracketed sum by spreading — one copy of a lands on b, another copy lands on c, and then you add the two products.
The rectangle picture makes this unmistakeable.
You are not swapping anything. You are not regrouping anything. You are taking a single factor and distributing it — handing a copy of a to each addend. That is why the law has its name.
Side by side — one table
Lined up, the three look like this. The difference is in what they rearrange.
| Law | Pattern | What moved |
|---|---|---|
| Commutative | a + b = b + a | the two items swapped places |
| Associative | (a + b) + c = a + (b + c) | the bracket slid from left pair to right pair |
| Distributive | a(b + c) = ab + ac | one factor spread across two addends |
Everything else — expanding 2(x + 3), collecting like terms in 4x + 7x, rearranging 5 + x + 3 into x + 8 — is a sequence of these three moves applied one after another. Naming the move you just made is the difference between algebra as rule-following and algebra as a language you can speak.
One warning
Distributivity is directional. Multiplication distributes over addition. Addition does not distribute over multiplication. Try it with numbers: 2 + (3 \times 4) = 14, but (2 + 3) \times (2 + 4) = 30. Nothing equal about those. Why: distributivity is saying "a rectangle of area a(b+c) splits into two rectangles." There is no analogous picture for "a number added to a product splits into two products" — because that statement is false.
If you ever catch yourself writing a + (b \cdot c) = (a + b)(a + c), pause. You have used a law that does not exist.
Related: Operations and Properties · Algebraic Identities · Real Numbers and Their Properties · Number Systems