When we use more than one adjective before a noun, which are one idea, we connect them with a hyphen.
- He is a good-looking man.
(The meaning is not good man and looking man. The meaning is a man that looks good. They are one idea.) - The slow-moving train arrived late.
(A train that is slow moving – it is one idea.) - I have a 500-year-old tree.
When the adjectives before the noun are different ideas we don’t use a hyphen.
- A black plastic cooking utensil.
(The utensil is black, the utensil is plastic, the utensil is for cooking. They talk about different parts of the utensil and so they are different ideas.) - A large smooth Chinese ceramic pot.
(A pot that is large, is smooth, is Chinese and is ceramic – different ideas.) - A large yellow T-shirt.
When the adjectives come after the noun, we don’t use a hyphen.
Compare:
- The blue-eyed cat has just had a bath.
(adjectives/blue-eyed, noun/cat)
The cat with blue eyes has just had a bath.
(noun/cat, adjectives/blue eyes) - The slow-moving train arrived late.
The train was slow moving, so it arrived late.