I cannot tell which is a predicate adjective:

He looks ill today.

He looks disdianfully at the pile of laundry.

Ill or Disdainfully?

"Ill" is correct; "disdainfully" is an adverb, so it can't be any kind of adjective!

Think of predicate adjectives as words that are describing the subject from the other side of the linking verb.

Here are some examples:

He is tall. ("tall" modifies "He")
The book is old. ("old" modifies "book")

There are some words in addition to forms of the verb "to be" that can be linking verbs -- to seem, to look, etc.
http://grammar.ccc.commnet.edu/grammar/verbs.htm#linking

thank you so much!!!

To determine which word is a predicate adjective in the given sentences, we need to understand what a predicate adjective is.

A predicate adjective is an adjective that follows a linking verb (such as "is," "am," "are," "was," "were," "appear," "seem," etc.) in a sentence and modifies the subject.

In the first sentence, "He looks ill today," the linking verb is "looks," and the word "ill" is the predicate adjective. We can identify it as a predicate adjective because it comes after the linking verb "looks" and describes the subject "he."

In the second sentence, "He looks disdainfully at the pile of laundry," the word "disdainfully" is not a predicate adjective. It is an adverb describing how "he" is looking at the pile of laundry. Adverbs modify verbs, adjectives, or other adverbs, but in this case, it modifies the verb "looks" by describing how he is doing the action.

So, in the given sentences, "ill" is the predicate adjective in the first sentence, while "disdainfully" is an adverb modifying the verb "looks" in the second sentence.