Hors d'oeuvres (pronounced "or-DERVS") are small one- or two-bite items that are served before dinner, usually accompanied by cocktails. As well, hors d'oeuvres may be served at a cocktail party where a full dinner is not being served. Hors d'oeuvres can be served at a table or passed on trays among guests.
Note that the word appetizer is sometimes used interchangeably with the word hors d'oeuvres, which can lead to confusion in cases where the word appetizer is understood to mean the first course of a meal. There's no hard and fast rule, but in general, an hors d'oeuvre is served before a meal, and an appetizer is part of a meal.
Technically, the word hors d'oeuvre, without an 's' at the end, can be used to indicate the singular and also the plural form of the word, but in America, at least, it's normal to say hors d'oeuvres (plural) to mean more than one.
Types of Hors d'Oeuvres
There are a few general categories of hors d'oeuvres. Canapés are a type of hors d'oeuvre constructed of a base of bread, pastry, crackers, or something similar, with some sort of spread such as flavored cream cheese or butter, and then a topping. The topping can be practically any sort of meat, seafood, vegetable, fruit, and so on. Think of crab and avocado toasts, bruschetta with olive tapenade and mushrooms, or toasts topped with tuna and red pepper mousse.
Another sort of hors d'oeuvres would be small items served on a skewer, stick, or toothpick such as grilled shrimp, satay beef skewers, or cheese and fruit kebabs. These can be artistically arranged, alternating items for color as well as a blend of flavors, or the sticks can be dedicated to one item.
Small pastry shells filled with some savory or sweet ingredient would also be a type of hors d'oeuvre. An elegant example is caviar and creme fraiche tarts, while a simple one would be mini-quiches. Small fried items such as turnovers, empanadas, samosas, and egg rolls are often served with a dipping sauce.
Crudité platters (cut raw vegetables served with a dip) or even dips served with crackers or chips can be considered hors d'oeuvres as well. Indeed, a simple bowl of nuts would be hors d'oeuvres if served with drinks before dinner. Think of a dish of citrus-marinated olives served with crackers or gougeres.
Deviled eggs are a classic, crowd-pleasing hors d'oeuvre that has many variations. There's really no limit to what sort of item can be considered an hors-d'oeuvre, provided it is small (one to two bites) and is served before dinner or in place of dinner at a cocktail party.
Hors d'Oeuvre Etiquette for Hosts and Guests
Be sure to provide your guests with what they need to eat hors d'oeuvres without mishap. At a minimum, guests will need a napkin and a small plate they can use to hold the items. Make provisions for disposal of any sticks, shells, shrimp tails, and used paper napkins.
Many hors d'oeuvres are finger foods and it is appropriate to eat them while standing and mingling. As a guest, note where the trashcan or disposal plate is located. Don't leave any items on clean tablecloths or countertops if you can avoid doing so.