Conditions nécessaires et suffisantes
1 · Necessary: the outcome needs the condition
Read A seulement si B as “A requires B”. From A you can infer B. From B alone, A remains open.
| une condition nécessaire | a prerequisite |
| il faut… | it is necessary to… |
L’accès est autorisé seulement si la réservation est confirmée.Access is allowed only if the booking is confirmed.
2 · Sufficient: the condition establishes the outcome
Read Si A, alors B as “A is enough for B” under the stated rule. This leaves other routes to B possible.
| une condition suffisante | a condition that is enough |
| il suffit de… | it is enough to… |
Pour recevoir le programme par courriel, il suffit d’en faire la demande.To receive the programme by email, you only need to request it.
3 · Both: the two directions hold
Si et seulement si gives an equivalence: each side implies the other. Keep the exact outcome in view.
Le statut « complet » est attribué si et seulement si toutes les pièces demandées ont été reçues.The status “complete” is assigned if and only if all the requested documents have been received.
4 · Necessary together does not automatically mean sufficient
A list of required conditions gives prerequisites. To present the whole list as enough, the rule must also establish that sufficiency.
Ces trois conditions sont nécessaires ; le texte ne précise pas si elles sont suffisantes.These three conditions are necessary; the text does not specify whether they are sufficient.