noun

• (organic chemistry, physical chemistry) A number of atoms in a series, which combine to form a molecule.
  "side chain"
• (surveying) A series of interconnected links of known length, used as a measuring device.
• (surveying) A long measuring tape.
• (mathematics, set theory, order theory) A totally ordered set, especially a totally ordered subset of a poset.
  "We first find an approximation of the chain partition, i.e. a small but not minimum size set of chains which cover all elements of the poset."

verb

• (transitive) To fasten something with a chain.
  "You should chain your bicycle to the railings to protect it from being stolen."
• (figurative) To connect as if with a chain, due to dependence, addiction, or other feelings
  "Sometimes I feel like I'm chained to this computer."
• (intransitive) To link multiple items together.
• (transitive) To secure someone with fetters.