Wiktionary:Word of the day/October 21

1. A common, firm, round fruit produced by a tree of the genus Malus.
   1. The fruit of the tree Malus domestica, chiefly with a green, red, or yellow skin, cultivated in temperate climates for cidermaking, cooking, and eating.
   2. Often with a qualifying word: any fruit or vegetable, or any other thing (such as a cone or gall) produced by a plant, especially if from a tree and similar to the fruit of Malus domestica (sense 1.1).
   3. Something which resembles the fruit of Malus domestica (sense 1.1) in shape (such as a ball, breast, or globe) or colour.
      1. Short for Adam's apple (“the lump in the throat, usually more noticeable in men than in women; the laryngeal prominence”).
      2. Short for apple-green (“a bright green colour with a light tint of yellow, like that of a Granny Smith apple”).

         apple:  

      3. (historical) Short for apple of the eye (“the pupil, or pupil and iris, of the eye, originally believed to be spherical; also, the eyeball”).
      4. (informal) The round, fleshy part of a cheek between the eye and the corner of the mouth when a person is smiling.
      5. (geometry) The surface of revolution of a circular arc of an angle greater than 180° rotated about the straight line passing through the arc's two endpoints.
      6. (smoking) In full apple bowl: a round bowl of a tobacco pipe; also, a tobacco pipe with such a bowl.
      7. (obsolete, baseball, slang) In full old apple: a baseball.
   4. (Christianity) According to postbiblical Christian tradition, the fruit of the tree of knowledge which was eaten by Adam and Eve despite God commanding them not to do so; the forbidden fruit.
   5. (obsolete, botany) Synonym of pome (“a type of fruit in which the often edible flesh arises from the swollen base of the flower and not from the carpels”)
3. A tree of the genus Malus; especially Malus domestica which is cultivated for its edible fruit; the apple tree.
4. Synonym of applewood (“the wood of the apple tree”)

apple v

1. (transitive) To make (something) appear like an apple (noun sense 1.1).
2. (intransitive)
   1. To become like an apple.
   2. (UK, dialectal, rare) To collect fir-cones.
   3. (obsolete except UK, dialectal) Of a flower bud or vegetable (especially a root vegetable): to grow into the shape of an apple.

Today is Apple Day in the United Kingdom, which celebrates apples and orchards. It was first organized by Common Ground, a charity encouraging people to engage with their local environment, on this date in 1990.