For Elementary / Intermediate English Learners

[EDIT]: Please note that this concept is more of a theory, but it still holds some very substantial truth behind it. This topic does not cover adjectives that fall in the same category or rare exceptions of this rule.

In many languages, the order of adjectives that describe a single noun doesn't matter. In English it does. If you do it wrong, you still get the point across, but it might not sound right. Many native English speakers still struggle with this, and most of us don't even know we unconsciously word things this way. Here's how you do it...

[opinion], [size], [age], [shape], [color], [origin], [material], [purpose], [Noun]

For example, you could have a "lovely little old rectangular green French silver whittling knife", and that would sound fine. But, you can't have "iron new pots" because [age] comes before [material]. This would better be said as "new iron pots".

The example above about the knife is not something you would generally read or hear, but it's still grammatically correct and makes sense. Usually when describing an object, you want to follow the rule of 3's, meaning that you use a maximum of three adjectives before a noun. You could then continue to describe the object in following sentences. You might better describe the knife like this:

"I have a little silver whittling knife that I got from my grandfather. It has a green handle and I believe it came from France! It's very old and a bit rectangular shaped, but it still works surprisingly well for its age!"

Notice how I used only three adjectives first to describe the knife, then I continued to describe other aspects of it in the following sentences. Also note how I never described it as 'lovely' because your opinion of an object can usually be derived from how you talk about it. Here, it can be obvious that I think it's a very good knife because 1.) I'm talking about the knife in more than one or two brief sentences, and 2.) my comment on how sharp the knife is suggests that I may like using it because of this quality.

The reasoning behind this whole 'order of adjectives' is that we put things that we care about the most first. We put attributes like [size], [age], [shape] and [color] first because those attributes describe how the object generally looks. Other attributes like [origin], [material] and [purpose] are of secondary importance. We like to list things that describe how an object looks first because it's easier to know what something is once we know what it looks like. [Origin], [material] and [purpose] don't give you this kind of general information.

Sometimes you can switch attributes around depending on what you want to emphasize in the sentence. The two groups of things we put first (size, age, shape and color) and things we put last (origin, material and purpose) are generally never switched around, but attributes within the first group can be. For example, if I want to emphasize the color of an object along with describing it's shape, I may put the color before the shape along with using the word 'very' for emphasis. "It's a very green rectangular knife" sounds much better than "It's a rectangular, very green knife". The following phrases are also permissible:

"A very old little knife"

"A very rectangular little knife"

"A very green little knife"

"A very rectangular old knife"

"A very green old knife"

Please comment below if you have any questions about this or would like me to phrase something in a simpler sentence for you!