Cross, a word with a great variety of meanings, is also at the head of an extensive family of words, some of which are listed and defined in this post.
Cross made its way into English circuitously from the Latin word crux, with stops in Old Irish and Old Norse. It originally referred to a post with a crossbeam on which condemned prisoners were hung to be executed. By its association with the execution of Jesus in such circumstances, it became a symbol of Christianity, not only as a t-shaped object but also as a series of gestures that collectively suggest the shape of the cross and are intended to convey an appeal to Jesus Christ for a blessing.
Capitalized, the word refers to the specific cross on which the execution took place; in this way, it is also a metonym for the Christian religion. (A metonym is a figure of speech in which a detail associated with an entity or an idea represents the entire entity or idea.) Metaphorically, in the phrase “cross to bear,” the word also suggests a personal trial, evoking the story that Jesus was forced to drag his cross over his shoulder to the site of his execution.
Cross also refers to any similarly shaped object or sign or to an x used as a signature. The word also denotes an act of hybridizing, or crossbreeding, living things or an animal that is a result of hybridization, as well as an intersection, a boxing punch, or a diagonal or lateral pass in soccer or any similar activity, as in a movement onstage during a theatrical performance. The word also pertains to an opposing or thwarting of an intention or to a dishonest or fraudulent contest or practice.
Verb and adjectival forms apply to these definitions as well, and the adjective across means “over,” “through,” or “on the opposite side of,” as well as “throughout,” and pertains to intersecting or passing through at an angle. (Across is also an adverb, as in “Walk across the field.”)
A crusade was originally a military expedition undertaken to assert political and religious control over the region of the Middle East associated with early Christianity; the series of such efforts that occurred during the Middle Ages is referred to as the Crusades. By extension, a crusade is any enthusiastic enterprise.
The noun crucifixion, as well as the verb crucify, refers to execution on a cross; the verb also refers metaphorically to ridiculing, scorning, or tormenting someone in the public arena.
Cruciform means “cross shaped,” a crucifer is a person who carries a cross in a religious procession or one of a family of edible plants (and a crozier is a symbolic shepherd’s crook carried by certain Christian clerics); cruciferous describes a specimen in the latter category. A cruciverbalist, meanwhile, is a preparer of crossword puzzles.
Other words stemming from crux include the use of the Latin term in English to refer to a difficult or unsolved problem or an essential point or main feature; the resulting adjective crucial means “decisive” or “significant,” and excruciating is an adjective meaning “agonizing” or “extreme” and refers usually to pain but sometimes to psychologically uncomfortable situations or to unpleasant emotions such as boredom.
As seen in a couple examples above, cross is also employed as the first element in a compound word. Other examples include crosswalk and crosswind; most of these are treated as closed compounds, but there are exceptions, including cross-eye and cross-stitch. Occasionally, cross is the second element, as in double-cross.
Crucible appears to be related but is not; it derives from the Latin term crucibulum, referring to an earthen pot in which metals are melted. That function, and perhaps the resemblance to words stemming from crux that begin with the element cruc-, led to the connotation of a test or trial or a situation in which significant change occurs.