Vinaigrette vs. sauce vs. assaisonnement

In French cuisine, 'vinaigrette', 'sauce', and 'assaisonnement' are all related to salad dressings, but they have distinct meanings and uses.

Vinaigrette

'Vinaigrette' is a specific type of salad dressing made primarily with oil and vinegar, often with added herbs and seasonings.
J'ai préparé une vinaigrette au citron pour la salade verte.
(I prepared a lemon vinaigrette for the green salad.)
La vinaigrette balsamique se marie bien avec la salade de tomates.
(Balsamic vinaigrette pairs well with tomato salad.)

Sauce

'Sauce' is a more general term for a liquid or semi-liquid condiment or dressing, which can be used for salads but also for many other dishes.
La sauce César est parfaite pour cette salade de poulet.
(Caesar sauce is perfect for this chicken salad.)
J'ai ajouté une sauce crémeuse à l'avocat sur ma salade.
(I added a creamy avocado sauce to my salad.)

Assaisonnement

'Assaisonnement' refers to seasoning or flavoring in general, which can include dressings for salads but also spices, herbs, and other flavor enhancers for any dish.
L'assaisonnement de cette salade est un mélange d'herbes fraîches.
(The seasoning of this salad is a mix of fresh herbs.)
Un bon assaisonnement peut transformer une simple salade en plat délicieux.
(Good seasoning can transform a simple salad into a delicious dish.)

Summary

While 'vinaigrette' specifically refers to an oil and vinegar-based dressing, 'sauce' is a broader term for various liquid condiments, and 'assaisonnement' encompasses all types of seasonings, including but not limited to salad dressings.