Dill (Anethum graveolens) is an annual herb in the celery family Apiaceae.
It is the sole species of the genus Anethum.
Fresh and dried dill leaves (sometimes called "dill weed" to distinguish it from dill seed) are widely used as herbs in Europe and central Asia.
Like caraway, the fernlike leaves of dill are aromatic and are used to flavor many foods such as gravlax (cured salmon) and other fish dishes, borscht and other soups, as well as pickles (where the dill flower is sometimes used). Dill is best when used fresh as it loses its flavor rapidly if dried; however, freeze-dried dill leaves retain their flavor relatively well for a few months.
Dill seed, having a flavor similar to caraway but also resembling that of fresh or dried dill weed, is used as a spice. Dill oil is extracted from the leaves, stems and seeds of the plant. The oil from the seeds is distilled and used in the manufacturing of soaps. 
Dill is the eponymous ingredient in dill pickles: cucumbers preserved in salty brine and/or vinegar.
In central and eastern Europe, Scandinavia, Russia and Finland, dill is a popular culinary herb used in the kitchen along with chives or parsley. Fresh, finely cut dill leaves are used as topping in soups, especially the hot red borsht and the cold borsht mixed with curds, kefir, yoghurt, or sour cream, which is served during hot summer weather and is called okroshka. It is also popular in summer to drink fermented milk (curds, kefir, yoghurt, or buttermilk) mixed with dill (and sometimes other herbs).
In the same way, prepared dill is used as a topping for boiled potatoes covered with fresh butter – especially in summer when there are so-called "new", or young, potatoes. The dill leaves can be mixed with butter, making a dill butter, which can serve the same purpose. Dill leaves mixed with tvorog form one of the traditional cheese spreads used for sandwiches. Fresh dill leaves are used all year round as an ingredient in salads, e.g., one made of lettuce, fresh cucumbers and tomatoes, the way basil leaves are used in Italy and Greece.
In Poland, fresh dill leaves mixed with sour cream are the basis for dressings. It is especially popular to use this kind of sauce with freshly cut cucumbers, which practically are wholly immersed in the sauce, making a salad called "mizeria". The dill leaves serve as a basis for cooking dill sauce, used hot for baked freshwater fish and for chicken or turkey breast, or used hot or cold for hard-boiled eggs.
In south-eastern Poland it is popular to cook a dill-based soup (zupa koperkowa), served with potatoes and hard-boiled eggs. Whole stems including roots and flower buds are traditionally used to prepare Polish-style pickled cucumbers (ogórki kiszone), especially the so-called low-salt cucumbers ("ogórki małosolne"). Whole stems of dill (often including the roots) are also cooked with potatoes, especially the potatoes of autumn and winter, so they resemble the flavor of the newer potatoes found in summer. Some kinds of fish, especially trout and salmon, are traditionally baked with the stems and leaves of dill.
In the Czech Republic, white dill sauce made of cream (or milk), butter, flour, vinegar and dill is called koprová omáčka (also koprovka or kopračka) and is served either with boiled eggs and potatoes or with dumplings and boiled beef. Another Czech dish with dill is a soup called kulajda that contains mushrooms (traditionally wild ones).
In Germany, dill is popular as a seasoning for fish and many other dishes, chopped as a garnish on potatoes, and a flavoring in pickles.
In Romania dill (mărar) is widely used as an ingredient for soups such as borş (pronounced "borsh"), pickles and other dishes, especially those based on peas, beans and cabbage. It is popular for dishes based on potatoes and mushrooms and can be found in many summer salads (especially cucumber salad, cabbage salad and lettuce salad). During springtime, it is used with spring onions in omelets. It often complements sauces based on sour cream or yogurt and is mixed with salted cheese and used as a filling. Another popular dish with dill as a main ingredient is dill sauce, which is served with eggs and fried sausages.
In Hungary, dill is very widely used. It is popular as a sauce or filling, especially in Langos, and mixed with a type of cottage cheese. Dill is also used for pickling and in salads. The Hungarian name for dill is kapor.
In Serbia, dill is known as mirodjija and is used as an addition to soups, potato and cucumber salads and French fries. It features in the Serbian proverb "бити мирођија у свакој чорби" /biti mirodjija u svakoj čorbi/ (to be a dill in every soup) which corresponds to the English proverb "to have a finger in every pie".
In Greece, dill is known as 'άνηθος' (anithos). In antiquity it was used as an add-in in wines, which they were called "anithites oinos" (wine with anithos-dill). In modern days, dill is used in salads, soups, sauces, and fish and vegetable dishes.
In Santa Maria, Azores, dill (endro) is the most important ingredient of the traditional Holy Ghost soup (sopa do Espírito Santo). Dill is found practically everywhere in Santa Maria and is curiously rare in the other Azorean Islands.
In Sweden, dill is a common spice or herb. The top of fully grown dill is called krondill (English: Crown dill); this is used when cooking crayfish. The krondill is put into the water after the crayfish is boiled, but still in hot and salt water. Then the entire dish is stored in refrigerator for at least 24 hours before eating (with toasted bread and butter). Krondill is also used for cucumber pickles. Small cucumbers, sliced or not, are put into a solution of hot water, mild acetic vinegar (not made from wine and without colour), sugar and krondill. After a month or two, the cucumber pickles are ready to eat, for instance, with pork, brown sauce and potatoes, as a "sweetener". The thinner part of dill and young plants may be used with boiled fresh potatoes (as the first potatoes for the year, which usually are small and have a very thin skin). It is used together with, or instead of other green herbs, like parsley, chives and basil, in salads. It is also often paired up with chives when used in food. Dill is often used to flavour fish and seafood in Sweden, for example gravlax and various herring pickles, among them the traditional sill i dill (literally "herring in dill"). In contrast to the various fish dishes flavoured with dill, there is also a traditional Swedish dish called dillkött, which is a meaty stew flavoured with dill. The dish commonly contains either pieces of veal or lamb that are boiled until tender and then served together with a vinegary dill sauce. Dill seeds may be used in breads or akvavit. A newer, non-traditional use of dill is paired up with chives as a flavouring of potato chips. This flavour of potato chips called "dillchips" is quite popular in Sweden.