пре него што / пошто

1. 'Before' Clauses: пре него што

The canonical conjunction used to express 'before' with a finite verb is пре него што:

• Опери руке пре него што седнемо за сто. (Wash your hands before we sit at the table.)
• Закључао сам врата пре него што сам отишао. (I locked the door before I left.)

Using just пре него (omitting што) is also fully standard and recognized in literary Serbian, while пре но што and пре но serve as older stylistic or literary alternatives. In non-past contexts referring to future actions, Serbian standardly uses the perfective present or футур II.

2. 'After' Clauses: пошто (Temporal vs. Causal)

While пошто is widely used to mean 'since / because', in formal narrative and written Serbian it also serves as a temporal conjunction meaning 'after' or 'once'.

To use temporal пошто accurately, keep three essential guidelines in mind:

• Aspect tendency: Temporal пошто typically takes a completed, perfective verb (свршени вид) to mark an event that has finished prior to the main event:
  Пошто је попио кафу, кренуо је на посао. (After he drank his coffee, he set off for work.)
  Imperfective verbs (несвршени вид) may appear temporally only in specific contexts denoting a bounded durative activity prior to the main event (e.g., Пошто је читао цео сат, одлучио је да прошета).
• Clause position: Temporal пошто either appears at the beginning of the sentence (preceding the main clause) or stands in a medial, interposed position between the main clause subject and verb (e.g., Марко је, пошто се спаковао, отишао на станицу). In contrast, it resists coming after the main clause (postposition); when placed after the main clause, native speakers will virtually always interpret пошто as causal ('because / since'). For postposed temporal 'after' clauses, use након што or када instead.
• Causal flexibility: Unlike temporal пошто, causal пошто ('since / because') freely takes both imperfective and perfective verbs (e.g., Пошто је пао испит, мора опет да учи — 'Since he failed the exam, he has to study again'). Thus, position and context work alongside verb aspect to clarify whether 'after' or 'since' is meant.

3. Clause Order and Punctuation

Punctuation depends on clause position and the type of clause:
• Inverted order (subordinate clause first): When either temporal clause precedes the main clause, a comma is mandatory:
  – Пре него што кренемо, морамо узети кључеве.
  – Пошто смо завршили ручак, наручили смо кафу.
• Interposed order (subordinate clause embedded): When temporal пошто is embedded medially within the main clause, it is enclosed in commas:
  – Петар је, пошто је прочитао писмо, одмах одговорио.
• Standard order (main clause first): Restrictive temporal clauses following the main clause do not take a comma (e.g., Закључао сам врата пре него што сам отишао). However, causal clauses following the main clause always take a comma according to standard orthography (e.g., Остаћемо код куће, пошто пада киша).