It illustrates a fixed verb–preposition construction whose meaning is literal, not idiomatic, and is frequently used to express empathy toward someone or something.

It is an idiomatic collocation interchangeable with “regret about,” and it requires the object to be an abstract noun rather than an animate entity.

It belongs to the category of strong collocations where substitution of the verb (feel) by near-synonyms like sense or experience is normally acceptable without altering meaning.

It represents a free combination of words with no restrictions, since both “sorry” and “for” can freely combine with a wide variety of verbs in English.

It demonstrates a restricted collocation, where sorry collocates with specific verbs (feel, be, sound, look), and the structure tends to convey a pragmatic idea of empathy or mild pity