Some adjectives are only used in predicative position. That means they go after be and other copular verbs (e.g. seem, look, become, turn, feel etc.). Adjectives that are only used in the predicative position usually begin with the letter a. Examples are: afloat, afraid, alright, alike, alive, alone, asleep and awake. In the attributive position (before a noun), we use other words or phrases to express the same idea.

She read for a while and then fell asleep.

Do not disturb a sleeping baby. (BUT NOT Do not disturb an asleep baby.)

The vessel is still afloat.

A floating leaf (BUT NOT an afloat leaf)

Afloat cannot be used before a noun.

He was afraid.

John is a frightened man. (NOT John is an afraid man.)

Afraid cannot be used before a noun.

The adjectives ill and well are mostly used in the predicative position. Before a noun, we use other words with similar meanings.

He is very well.

He is a healthy man. OR He is a fit man. (NOT He is a well man.)

She is ill.

Who looks after sick people? (NOT Who looks after ill people?)

Ill is not normally used before a noun.