Abbreviated adverbial clauses introduced by subordinators represent an important means of condensation, making it possible to express explicitly the semantic relation obtaining between the superordinate and the subordinate clause, or at least substantially narrowing the possibilities of interpretation. “An introduction of a condenser into a sentence also prevents repetition of some dynamically weak sentence elements.” (Hladký 1961, 114)
Condensation of an adverbial clause, while retaining the subordinator, may be achieved through the processes of nominalization (giving rise to noun phrases), non-finitization (nonfinite -ing clauses), or ellipsis (nonfinite -ed clauses, and verbless clauses).
The factors which may hinder or block the condensation are connected partly with the subordinator itself, different subordinators licensing different types of complement. The subordinators seem to form a gradient of possible complementation with those which may also function as prepositions, e.g. after, at one end, and prototypical conjunctions at the other, e.g. when. The constraints on abbreviation may be connected with the type of underlying subject of the nonfinite or verbless clause, its relatedness to the clause elements of the superordinate clause, and sometimes the surrounding cotext, being the decisive factor. Another factor precluding abbreviation may be the semantic characteristics of the verb in the subordinate clause. Last but not least, a relevant factor in this respect is the position of the subordinate clause in the sentence.