-чий

1. The Nature of -чий Adjectives
While these words originate from verbs, they have undergone adjectivization (adjectivization). In Ukrainian linguistics, these are formally known as активні дієприкметники теперішнього часу, що перейшли в прикметники. This means they no longer express a process in time, but a permanent characteristic. For example, блискучий doesn't mean 'currently shining,' but 'brilliant' or 'outstanding' (like a brilliant career). These words often acquire figurative meanings, such as колючий погляд (a prickly/stinging look).

2. A Fixed Vocabulary, Not a Productive Rule
Historically, many of these adjectives were formed from verb stems, often resembling the 3rd person plural present tense (e.g., ревуть → ревучий 'roaring', лежать → лежачий 'bedridden'). However, in modern Ukrainian, this is not a productive rule. You should not apply it to create new words. Note that the transition to an adjective often involves a stress shift compared to the verb stem (e.g., пеку́чий 'stinging/burning' as an adjective vs. the verb печу́ть).

3. Technical and Scientific Contexts
While certain -чий forms appear in older literature, modern Ukrainian standards (DSTU) increasingly prefer native constructions. For instance, результуюча сила is now better expressed as рівнодійна сила (resultant force). Similarly, несучий гвинт (main rotor of a helicopter) is often replaced by тримальний гвинт. Note that a 'lead screw' in engineering is ходовий гвинт, not несучий.

4. The 'No Complements' Rule
A critical distinction is that these forms cannot take objects or prepositional phrases. Because they are adjectives, they can be modified by adverbs of degree like дуже (very). If you need to specify where or when the action is happening, you must use a relative clause with який or relative clause with що.

5. Register and Avoidance of Calques
Modern Ukrainian discourages inventing new -чий forms. Instead of діючий закон, use чинний закон (current law). While Спляча красуня (Sleeping Beauty) is a fixed traditional title, modern stylistic preferences often favor приспана красуня or зачарована красуня.