1. [n]  metal device shaped in such a way that when it is inserted into the appropriate lock the lock's mechanism can be rotated
2. [n]  a lever that actuates a mechanism when depressed
3. [n]  mechanical device used to wind another device that is driven by a spring (as a clock)
4. [n]  pitch of the voice; "he spoke in a low key"
5. [n]  something crucial for explaining; "the key to development is economic integration"
6. [n]  a list of words or phrases that explain symbols or abbreviations
7. [n]  any of 24 major or minor diatonic scales that provide the tonal framework for a piece of music
8. [n]  a coral reef off the southern coast of Florida
9. [n]  United States lawyer and poet who wrote a poem after witnessing the British attack on Baltimore during the War of 1812; the poem was later set to music and entitled `The Star-Spangled Banner' (1779-1843)
10. [n]  one thousand grams; the basic unit of mass adopted under the System International d'Unites; "a kilogram is approximately 2.2 pounds"; "they were carrying two keys of heroin"
11. [adj]  serving as an essential component; "a cardinal rule"; "the central cause of the problem"; "an example that was fundamental to the argument"; "computers are fundamental to modern industrial structure"
12. [adj]  effective; producing a desired effect; "the operative word"
13. [v]  harmonize with or adjust to; "key one's actions to the voters' prevailing attitude"
14. [v]  regulate the musical pitch of
15. [v]  identify as in botany or biology, for example
16. [v]  vandalize a car by scratching the sides with a key"; "His new Mercedes was keyed last night in the parking lot"
17. [v]  provide with a key; "We were keyed after the locks were changed in the building"

1. \Key\ (k[=e]), n. [OE. keye, key, kay, AS. c[ae]g.]
   1. An instrument by means of which the bolt of a lock is shot
      or drawn; usually, a removable metal instrument fitted to
      the mechanism of a particular lock and operated by turning
      in its place.
   2. An instrument which is turned like a key in fastening or
      adjusting any mechanism; as, a watch key; a bed key, etc.
   3. That part of an instrument or machine which serves as the
      means of operating it; as, a telegraph key; the keys of a
      pianoforte, or of a typewriter.
   4. A position or condition which affords entrance, control,
      pr possession, etc.; as, the key of a line of defense; the
      key of a country; the key of a political situation. Hence,
      that which serves to unlock, open, discover, or solve
      something unknown or difficult; as, the key to a riddle;
      the key to a problem.
            Those who are accustomed to reason have got the true
            key of books.                         --Locke.
            Who keeps the keys of all the creeds. --Tennyson.
   5. That part of a mechanism which serves to lock up, make
      fast, or adjust to position.
   6. (Arch.)
      (a) A piece of wood used as a wedge.
      (b) The last board of a floor when laid down.
   7. (Masonry)
      (a) A keystone.
      (b) That part of the plastering which is forced through
          between the laths and holds the rest in place.
   8. (Mach.)
      (a) A wedge to unite two or more pieces, or adjust their
          relative position; a cotter; a forelock. See Illusts.
          of {Cotter}, and {Gib}.
      (b) A bar, pin or wedge, to secure a crank, pulley,
          coupling, etc., upon a shaft, and prevent relative
          turning; sometimes holding by friction alone, but more
          frequently by its resistance to shearing, being
          usually embedded partly in the shaft and partly in the
          crank, pulley, etc.
   9. (Bot.) An indehiscent, one-seeded fruit furnished with a
      wing, as the fruit of the ash and maple; a samara; --
      called also {key fruit}.
   10. (Mus.)
       (a) A family of tones whose regular members are called
           diatonic tones, and named key tone (or tonic) or one
           (or eight), mediant or three, dominant or five,
           subdominant or four, submediant or six, supertonic or
           two, and subtonic or seven. Chromatic tones are
           temporary members of a key, under such names as ``
           sharp four,'' ``flat seven,'' etc. Scales and tunes
           of every variety are made from the tones of a key.
       (b) The fundamental tone of a movement to which its
           modulations are referred, and with which it generally
           begins and ends; keynote.
                 Both warbling of one song, both in one key.
                                                  --Shak.
   11. Fig: The general pitch or tone of a sentence or
       utterance.
             You fall at once into a lower key.   --Cowper.
   {Key bed}. Same as {Key seat}.
   {Key bolt}, a bolt which has a mortise near the end, and is
      secured by a cotter or wedge instead of a nut.
   {Key bugle}. See {Kent bugle}.
   {Key of a position} or {country.} (Mil.) See {Key}, 4.
   {Key seat} (Mach.), a bed or groove to receive a key which
      prevents one part from turning on the other.
   {Key way}, a channel for a key, in the hole of a piece which
      is keyed to a shaft; an internal key seat; -- called also
      {key seat}.
   {Key wrench} (Mach.), an adjustable wrench in which the
      movable jaw is made fast by a key.
   {Power of the keys} (Eccl.), the authority claimed by the
      ministry in some Christian churches to administer the
      discipline of the church, and to grant or withhold its
      privileges; -- so called from the declaration of Christ,
      ``I will give unto thee the keys of the kingdom of
      heaven.'' --Matt. xvi. 19.
   

2. \Key\, v. t. [imp. & p. p. {Keved}; p. pr. & vb. n.
   {Keying}.]
   To fasten or secure firmly; to fasten or tighten with keys or
   wedges. --Francis.
   {To key up}.
   (a) (Arch.) To raise (the whole ring of an arch) off its
       centering, by driving in the keystone forcibly.
   (b) (Mus.) To raise the pitch of.
   (c) Hence, fig., to produce nervous tension in.
   

3. \Key\, n. (Teleg.)
   A metallic lever by which the circuit of the sending or
   transmitting part of a station equipment may be easily and
   rapidly opened and closed; any device for closing or opening
   an electric circuit.
   

4. \Key\, n.
   A simplified version or analysis which accompanies something
   as a clue to its explanation, a book or table containing the
   solutions to problems, ciphers, allegories, or the like, or a
   table or synopsis of conspicuous distinguishing characters of
   members of a taxonomic group.
   

1. A value used to identify a record in a database, derived by applying some fixed function to the record. The key is often simply one of the fields (a column if the database is considered as a table with records being rows, see "key field"). Alternatively the key may be obtained by applying some function, e.g. a hash function, to one or more of the fields. The set of keys for all records forms an index. Multiple indexes may be built for one database depending on how it is to be searched.

2. A value which must be fed into the algorithm used to decode an encrypted message in order to reproduce the original plain text. Some encryption schemes use the same (secret) key to encrypt and decrypt a message, but public key encryption uses a "private" (secret) key and a "public" key which is known by all parties.

frequently mentioned in Scripture. It is called in Hebrew _maphteah_, i.e., the opener (Judg. 3:25); and in the Greek New Testament _kleis_, from its use in shutting (Matt. 16:19; Luke 11:52; Rev. 1:18, etc.). Figures of ancient Egyptian keys are frequently found on the monuments, also of Assyrian locks and keys of wood, and of a large size (comp. Isa. 22:22).

The word is used figuratively of power or authority or office (Isa. 22:22; Rev. 3:7; Rev. 1:8; comp. 9:1; 20:1; comp. also Matt. 16:19; 18:18). The "key of knowledge" (Luke 11:52; comp. Matt. 23:13) is the means of attaining the knowledge regarding the kingdom of God. The "power of the keys" is a phrase in general use to denote the extent of ecclesiastical authority.