When you need to emphasize strict rules or a necessary sequence of events, begin your sentence with a restrictive conditional clause using pas als (only if/when), pas toen (only when - past), or alleen wanneer (only when).
Pas als
Use pas als for strict conditions in the present or future. It introduces a subordinate clause, so its verbs go to the end. Because this entire clause occupies the first position in the sentence, the main clause that follows the comma must immediately start with its verb (inversion).
| Only if you show your boarding pass, are you allowed to go to the gate. | Pas als je je instapkaart toont, mag je naar de gate. |
| Only when we fly, are you allowed to turn on the laptop. | Pas als we vliegen, mag je de laptop aanzetten. |
Pas toen
Just as the standard conditional word als changes to toen for single events in the past, pas als becomes pas toen for strict sequences that have already happened. The word order rules remain exactly the same.
| Only when we had landed safely, were we allowed to grab the hand luggage. | Pas toen we veilig geland waren, mochten we de handbagage pakken. |
| Only when I stood at the gate, did I find my boarding pass. | Pas toen ik bij de gate stond, vond ik mijn instapkaart terug. |
Alleen wanneer
Another way to express "only when" or "only if" is with alleen wanneer. It behaves exactly like pas als.
| Only when the pilot is ready, will we take off. | Alleen wanneer de piloot klaar is, zullen we opstijgen. |
| Only when the pilot stops at the gate, is the door allowed to be open. | Alleen wanneer de piloot bij de gate stopt, mag de deur open. |
