a measuring instrument that sends out an acoustic pulse in water and measures distances in terms of the time for the echo of the pulse to return; "sonar is an acronym for sound navigation ranging"; "asdic is an acronym for antisubmarine detection investigation committee"
having a bearing on or connection with the subject at issue; "the scientist corresponds with colleagues in order to learn about matters relevant to her own research"
a subdivision of a written work; usually numbered and titled; "he read a chapter every night before falling asleep"
a series of related events forming an episode; "a chapter of disasters"
a local branch of some fraternity or association; "he joined the Atlanta chapter"
an ecclesiastical assembly of the monks in a monastery or even of the canons of a church
any distinct period in history or in a person's life; "the industrial revolution opened a new chapter in British history"; "the divorce was an ugly chapter in their relationship"
trade name of a company that produces musical recordings; "the artists and repertoire department of a recording label is responsible for finding new talent"
a brief description given for purposes of identification; "the label Modern is applied to many different kinds of architecture"
an identifying or descriptive marker that is attached to an object
a radioactive isotope that is used in a compound in order to trace the mechanism of a chemical reaction
distinguish (an element or atom) by using a radioactive isotope or an isotope of unusual mass for tracing through chemical reactions
distinguish (as a compound or molecule) by introducing a labeled atom
assign a label to; designate with a label; "These students were labelled `learning disabled'"
absolutely required and not to be used up or sacrificed
absolutely necessary; vitally necessary; "essential tools and materials"; "funds essential to the completion of the project"; "an indispensable worker"
being or relating to or containing the essence of a plant etc; "essential oil"