Update 2016-4-14: Fixed British Council link.
Different kinds of adjectives in English
Adjectives in English are not all the same, and what we can do with them is not always the same.
Some are gradable (or "graded"). You can have degrees of them ("a little", "rather", "very" etc.)
Some are non-gradable (or "ungradable" or "non-graded").
Some non-gradable adjectives have a very strong meaning. Some non-gradable adjectives are absolute (e.g. either you're dead or you're not dead. There's no middle ground).
You can't have degrees of non-gradable adjectives You can't be "a little" or "very" of a non-gradable adjectives.
Some adjectives can be either gradable or non-gradable, depending on the exact meaning in the context.
Knowing whether an adjective is gradable or non-gradable can be important for intensifying it (e.g. should you say "very" or "absolutely" to intensify "exhausted"?).
To make things even more complicated, some linguists refer to classifying & non-classifying adjectives. (E.g. either you're dead or you're not dead.) Linguists love to disagree about everything to do with language.
Introduction to Gradable & Non-Gradable Adjectives
English Club has a good introduction to this issue, with some examples.
The excellent Random Idea English blog has an article on why you should know about the difference between gradable & non-gradable adjectives, a quick introduction to them, and many useful exercises to learn and practise.
Warning for students in China: Random Idea English is hosted on Blogspot, and there might be a few problems due to the Great Firewall. The page might look a little strange, or sometimes be blocked completely.
How can you know if an adjective is gradable or not?
Unfortunately most English dictionaries do not yet have this info about adjectives. And there is no list with every single gradable and every single non-gradable adjective.
Random Idea English has an article with advice on how you can work out for yourself if an adjective is gradable or not.
One dictionary that does give info on whether an adjective is gradable or not is the Baidu online English-English & English-Chinese dictionary.
If an adjectives is gradable, it says:
If an adjective is not gradable, it just says:
Sometimes it doesn't say which type an adjective is, because the adjective doesn't have its own page; instead it is just treated as related to another part of speech (verb, noun etc), in which case the ADJ-GRADED or ADJ is not next to the adjective.
Here are some examples from the Baidu dictionary.
Intensifiers with gradable & non-gradable adjectives
The main difference with these adjectives is which intensifiers we use with them.
Random Idea English has a post dedicated to exercises on which intensifiers to use (although many of them are also part of the article on gradable and ungradable adjectives).
The British Council's Learn English site also has an article with an explanation of gradable and non-gradable adjectives and an exercise on intensifiers for them.
In my online classes
In my online English classes, I give info about words in the chat window, from notes that I prepare in advance. Slowly I am adding to my notes info on whether an adjective is gradable or not. It is a long, imperfect process, so please forgive me if I don't always says if an adjective is gradable or not, or if sometimes I make a mistake.
If you have anything to say on gradable / non-gradable adjectives or the links I've provided, please feel free to write a comment below.
G.A.L.E.S.L. / joe3
Some tips and links on learning English.