X-ray crystallography.noun
the method of using X-rays-diffraction for obtaining an exact picture of atoms in molecules to determine the structure of crystals or molecules

x-ray.noun
relatively high energy photon with wavelength in the approximate range from 0.01 to 10 nanometers; a  stream of such photons, used for their penetrating power in radiography, radiology, radiotherapy, and scientific research; also called roentgen ray; called 'x' because the discoverer Roentgen didn't know what else to call them
x-rayed, X-rayed, x-raying, X-raying, x-rays, X-rays.transitive verbs
to irradiate with x-rays; to photograph with x-rays

yawning.adjective
gaping open; cavernous (a yawning abyss)
yawningly.adverb
yawn.verb
yawned, yawning, yawns.intransitive verbs
to open the mouth wide with a deep inhalation, usually involuntarily from drowsiness, fatigue, or boredom; to open wide; gape.(the chasm yawned at our feet
transitive verb use.to utter wearily, while or as if while yawning ( yawned his disapproval of the silly bureaucrat
yawn.noun
the act of yawning
yawner.noun

yearning.noun
a persistent, often wistful or melancholy desire; a longing (the yearnings for romance and adventure that are awakened by spring)
yearn, yearned, yearning, yearns.intransitive verbs
to have a strong, often melancholy desire; to feel deep pity, sympathy, or tenderness (yearned over the poor child's fate)
yearner.noun
yearningly.adverb

yield, yielded, yielding, yields.verbs
transitive verb use.to give over possession of, as in deference or defeat; surrender; to give up (an advantage, for example) to another; concede; to give forth by or as if by a natural process, especially by cultivation (a field that yields many bushels of corn); to furnish as return for effort or investment; be productive of (an investment that yields high percentages); 
intransitive verb use.to give forth a natural product; be productive; to produce a return for effort or investment (bonds that yield well); to give up, as in defeat; surrender or submit; to give way to pressure or force (the door yielded to a gentle push); to give way to argument, persuasion, influence, or entreaty (the child pleaded, but the parents wouldn't yield; to give place, as to one that is superior (the government reluctantly yielded to the will of the people); 
yield.noun
an amount yielded or produced; a product; a profit obtained from an investment; a return; the energy released by an explosion, especially by a nuclear explosion, expressed in units of weight of TNT required to produce an equivalent release (the atomic bomb dropped on Hiroshima had a yield of 20 kilotons)
yielder.noun

yin.and.yang.nouns
the passive (yin) and active cosmic principles (from Asian dualistic philosophy)

yoga.noun
a Hindu discipline aimed at training the consciousness for a state of perfect spiritual insight and tranquillity; a system of exercises practiced as part of this discipline to promote control of the body and mind
yogic.adjective

yogi.noun,.plural.yogis.(pronounced 'yo gee', 'yo gees')
one who practices yoga; yogi is one who seeks union of body mind and environment
Yane Yoga.is yoga of knowledge

yoke.noun,.plural.yoke.or.yokes
a frame designed to be carried across a person's shoulders with equal loads suspended from each end; a crossbar with two U-shaped pieces that encircle the necks of a pair of oxen or other draft animals working together; a pair of draft animals, such as oxen, joined by a yoke; couple; a bar used with a double harness to connect the collar of each horse to the pole of a wagon or coach; a clamp or vise that holds a machine part in place or controls its movement or that holds two such parts together
Nautical - a crossbar on a ship's rudder to which the steering cables are connected; the condition of being subjugated or in bondage (the modern day world slaves under the yoke of monetary subjugation)
yoke, yoked, yoking, yokes.transitive verbs
to fit or join with a yoke; to harness a draft animal to; bind (partners who were yoked together for life); to force into heavy labor, bondage, or subjugation
intransitive verb use.to become joined securely

Yukon Territory

Z boson.noun
Z boson is an unchanged massive {91GeV/c² (c is the speed of light in a vacuum; ² is for it squared)-particle of the Weak Force.

zeal.noun
means intense.emotion.compelling action; implies energetic and unflagging pursuit of an aim or devotion to a cause (preaches with the zeal of the converted); eagerness and ardent interest in pursuit of something; fervor
synonym.passion

zealous.noun
filled with or characterized by zeal-(zealous missionaries)
zealously.adverb
zealousness.noun

zealot.noun
one who is zealous

zeitgeist.noun
the spirit of the time; the taste and outlook characteristic of a period or generation

zilch.noun
zero; nothing
zilch.adjective
amounting to nothing; nil (business was zilch)

zygote.noun
any cell formed by the union of two gametes (the marrying {Greek, 'gamos'} of a reproductive cell with another similar one to form the cell that develops into a new individual)