rotting vs rotten

Rotting is a present participle used in the continuous tenses.
e.g. The fallen apples are rotting under the tree.

Rotting can also be a noun as in:
The rotting of the fallen apple took place over weeks.

Rotten is a past participle used in two ways.
Firstly it is used in the perfect tenses.
e.g. The apples on the ground have rotten, so don't eat them.
Secondly it is used in the passive voice.
e.g. The apples were rotten by worms.

Rotten can also simply be an adjective as in:
A rotten apple does not taste good.

2008-08-23 08:35:50 補充：
但係我見D書係咁用: a rotting apple

點解既?
A rotten apple - an apple that has finished rotting (perfect tense)
A rotting apple - an apple that is still rotting (continuous tense)
Both are grammatically correct but have different meanings as above.

ROTTING is a verb and ROTTEN is an adjective.

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For example,


ROTTING--The boiled egg started rotting after four days.

ROTTEN--Nicky had stomach virus after she ate that rotten egg.