'Know' + 'WH'-Word + 'To'-Infinitive. Wh- clauses. After / Before: indicating time-relative activities. When-While: indicating time-relative activities. In traditional grammar, the adverbs when and while introduce adverbial clauses. They are called also called subordinating conjunctions which, in this case, join time-related clauses. The clause is called a dependent clause.
Note that in traditional grammar, a preposition requires an object, a noun or noun phrase, after it. All other types of complements such as an adverb phrase, infinitive phrase, gerund phrase, or clause are not included in the definition of a prepositional phrase. In linguistic description, the prepositions while, when, though, although, if, as if, as though, whenever, once and whilst may have as a complement: a finite clause, a nonfinite clause, or a verbless clause.
Temporal Location Adjuncts (after, before, since, when, while) — Prepositions (Huddleston 8 §6.3;697) — Conjunctions (Swan 73, 411.6, 30, 97) — Subordinator. Note that a large number of adverbs have been re-assigned to the category of preposition, which allows a wide range of complement type. Be supposed to. Green Level Quiz #5 - be supposed to.