1. [n]  a series of (usually metal) rings or links fitted into one another to make a flexible ligament
2. [n]  a necklace made by a stringing objects together; "a string of beads" or"a strand of pearls"
3. [n]  anything that acts as a restraint
4. [n]  metal shackles; for hands or legs
5. [n]  a number of similar establishments (stores or restaurants or banks or hotels or theaters) under one ownership
6. [n]  a series of things depending on each other as if linked together; "the chain of command"; "a complicated concatenation of circumstances"
7. [n]  a series of linked atoms (generally in an organic molecule)
8. [n]  a series of hills or mountains; "the valley was between two ranges of hills"; "the plains lay just beyond the mountain range"
9. [n]  British biochemist (born in Germany) who isolated and purified penicillin, which had been discovered in 1928 by Sir Alexander Fleming (1906-1979)
10. [n]  a unit of length
11. [v]  fasten or secure with chains; "Chain the chairs together"
12. [v]  connect or arrange into a chain by linking

1. \Chain\, n. [F. cha[^i]ne, fr. L. catena. Cf. {Catenate}.]
   1. A series of links or rings, usually of metal, connected,
      or fitted into one another, used for various purposes, as
      of support, of restraint, of ornament, of the exertion and
      transmission of mechanical power, etc.
            [They] put a chain of gold about his neck. --Dan. v.
                                                  29.
   2. That which confines, fetters, or secures, as a chain; a
      bond; as, the chains of habit.
            Driven down To chains of darkness and the undying
            worm.                                 --Milton.
   3. A series of things linked together; or a series of things
      connected and following each other in succession; as, a
      chain of mountains; a chain of events or ideas.
   4. (Surv.) An instrument which consists of links and is used
      in measuring land.
   Note: One commonly in use is Gunter's chain, which consists
         of one hundred links, each link being seven inches and
         ninety-two one hundredths in length; making up the
         total length of rods, or sixty-six, feet; hence, a
         measure of that length; hence, also, a unit for land
         measure equal to four rods square, or one tenth of an
         acre.
   5. pl. (Naut.) Iron links bolted to the side of a vessel to
      bold the dead-eyes connected with the shrouds; also, the
      channels.
   6. (Weaving) The warp threads of a web. --Knight.
   {Chain belt} (Mach.), a belt made of a chain; -- used for
      transmitting power.
   {Chain boat}, a boat fitted up for recovering lost cables,
      anchors, etc.
   {Chain bolt}
      (a) (Naut.) The bolt at the lower end of the chain plate,
          which fastens it to the vessel's side.
      (b) A bolt with a chain attached for drawing it out of
          position.
   {Chain bond}. See {Chain timber}.
   {Chain bridge}, a bridge supported by chain cables; a
      suspension bridge.
   {Chain cable}, a cable made of iron links.
   {Chain coral} (Zo["o]l.), a fossil coral of the genus
      {Halysites}, common in the middle and upper Silurian
      rocks. The tubular corallites are united side by side in
      groups, looking in an end view like links of a chain. When
      perfect, the calicles show twelve septa.
   {Chain coupling}.
      (a) A shackle for uniting lengths of chain, or connecting
          a chain with an object.
      (b) (Railroad) Supplementary coupling together of cars
          with a chain.
   {Chain gang}, a gang of convicts chained together.
   {Chain hook} (Naut.), a hook, used for dragging cables about
      the deck.
   {Chain mail}, flexible, defensive armor of hammered metal
      links wrought into the form of a garment.
   {Chain molding} (Arch.), a form of molding in imitation of a
      chain, used in the Normal style.
   {Chain pier}, a pier suspended by chain.
   {Chain pipe} (Naut.), an opening in the deck, lined with
      iron, through which the cable is passed into the lockers
      or tiers.
   {Chain plate} (Shipbuilding), one of the iron plates or
      bands, on a vessel's side, to which the standing rigging
      is fastened.
   {Chain pulley}, a pulley with depressions in the periphery of
      its wheel, or projections from it, made to fit the links
      of a chain.
   {Chain pumps}. See in the Vocabulary.
   {Chain rule} (Arith.), a theorem for solving numerical
      problems by composition of ratios, or compound proportion,
      by which, when several ratios of equality are given, the
      consequent of each being the same as the antecedent of the
      next, the relation between the first antecedent and the
      last consequent is discovered.
   {Chain shot} (Mil.), two cannon balls united by a shot chain,
      formerly used in naval warfare on account of their
      destructive effect on a ship's rigging.
   {Chain stitch}. See in the Vocabulary.
   {Chain timber}. (Arch.) See {Bond timber}, under {Bond}.
   {Chain wales}. (Naut.) Same as {Channels}.
   {Chain wheel}. See in the Vocabulary.
   {Closed chain}, {Open chain} (Chem.), terms applied to the
      chemical structure of compounds whose rational formul[ae]
      are written respectively in the form of a closed ring (see
      {Benzene nucleus}, under {Benzene}), or in an open
      extended form.
   {Endless chain}, a chain whose ends have been united by a
      link.
   

2. \Chain\, v. t. [imp. p. p. {Chained} (ch[=a]nd); p. pr. &
   vb. n. {Chaining}.]
   1. To fasten, bind, or connect with a chain; to fasten or
      bind securely, as with a chain; as, to chain a bulldog.
            Chained behind the hostile car.       --Prior.
   2. To keep in slavery; to enslave.
            And which more blest? who chained his country, say
            Or he whose virtue sighed to lose a day? --Pope.
   3. To unite closely and strongly.
            And in this vow do chain my soul to thine. --Shak.
   4. (Surveying) To measure with the chain.
   5. To protect by drawing a chain across, as a harbor.
   

1. (From BASIC's "CHAIN" statement) To pass control to a child or successor without going through the operating system command interpreter that invoked you. The state of the parent program is lost and there is no returning to it. Though this facility used to be common on memory-limited microcomputers and is still widely supported for backward compatibility, the jargon usage is semi-obsolescent; in particular, Unix calls this exec.

Compare with the more modern "subshell".

2. A series of linked data areas within an operating system or application program. "Chain rattling" is the process of repeatedly running through the linked data areas searching for one which is of interest. The implication is that there are many links in the chain.

3. A possibly infinite, non-decreasing sequence of elements of some total ordering, S

        x0 <= x1 <= x2 ...

A chain satisfies:

        for all x,y in S, x <= y \/ y <= x.

I.e. any two elements of a chain are related.

("<=" is written in LaTeX as \sqsubseteq).

[Jargon File]

(1.) A part of the insignia of office. A chain of gold was placed about Joseph's neck (Gen. 41:42); and one was promised to Daniel (5:7). It is used as a symbol of sovereignty (Ezek. 16:11). The breast-plate of the high-priest was fastened to the ephod by golden chains (Ex. 39:17, 21).

(2.) It was used as an ornament (Prov. 1:9; Cant. 1:10). The Midianites adorned the necks of their camels with chains (Judg. 8:21, 26).

(3.) Chains were also used as fetters wherewith prisoners were bound (Judg. 16:21; 2 Sam. 3:34; 2 Kings 25:7; Jer. 39:7). Paul was in this manner bound to a Roman soldier (Acts 28:20; Eph. 6:20; 2 Tim. 1:16). Sometimes, for the sake of greater security, the prisoner was attached by two chains to two soldiers, as in the case of Peter (Acts 12:6).