dictum.noun
a formal statement of opinion

didactic.adjective
designed or intended to teach; intended to convey instruction and information as well as pleasure and entertainment; making moral observations 
didacticism.noun
didactical.adjective
didactically.adverb

die hard.idiom
to resist against overwhelming, hopeless odds; to take a long time in passing out of existence (prejudices that die hard)

differentiate.transitive verb
to constitute a difference in or between
differentiation.noun
a differentiation or being differentiated

diffident.adjective
lacking in confidence; shy

diffuse, diffused, diffusing, diffuses.verbs-–-transitive-and.intransitive-use
transitive-to pour out and cause to spread freely; to spread about or scatter; disseminate; to make less brilliant; soften
intransitive-to become widely dispersed; spread out
diffuse.adjective
widely spread or scattered; not concentrated
diffusely.adverb
diffuseness.noun

diffusion.noun
the process of diffusing or the condition of being diffused

diffraction
the bending or spreading of waves

dignified.adjective
having or showing dignity or stateliness

dignity.noun,.plural.dignities
the quality or state of being worthy of esteem or respect; of merit, worth; worthiness; stateliness; inherent nobility and worth (the dignity of honest labor); poise and self-respect; stateliness and formality in manner and appearance; the respect and honor associated with an important position; a high office or rank; dignities; the ceremonial symbols and observances attached to high office
dignity.transitive verb
worthiness; a person's degree of worth; worthy of respect

dilemma.noun
a situation where one must choose between unpleasant alternatives
dilemmatic.adjective

diligent.adjective
characterized by directed, steady, earnest, and energetic effort; painstaking 
diligently.adverb
synonym.busy

diligence.noun
earnest and persistent application to an undertaking; steady effort; assiduity; attentive care; heedfulness

dimension.noun
any measurable extent, as, length, breadth, thickness, etc.; extent; size; degree; the number of coordinates (to set in equal rank; that which enables coordination) needed to specify the position of a point in some space of possibilities. Compare heterotic string theory

diminish, diminished, diminishing, diminishes.transitive verbs
to make smaller, reduce in size, degree importance, etc. 
diminish.intransitive verb
to become smaller 
diminished, diminishable.adjectives
made smaller, lessened, reduced
diminishment.noun

diminution.noun
the act or process of diminishing; a lessening or reduction; the resulting reduction; decrease
Music.-.repetition of a theme in notes one-quarter or one-half the duration of the original.
diminutional.adjective

diminutive.noun
a diminutive word, affix, or name; a diminutive individual
diminutive.adjective
indicating small size and sometimes the state or quality of being familiarly known, lovable, pitiable, or contemptible – used of affixes (-ette, -kin, -ling) and of words formed with them (as kitchenette, duckling, etc.), of clipped forms (as Jim), and of altered forms (as Peggy) – compare augmentative; exceptionally or notably small; tiny 
diminutively.adverb
diminutiveness.noun
synonym-small

dinoflagellates.noun
any of bioluminescent numerous minute, chiefly marine protozoans of the order Dinoflagellata, characteristically having two flagella and a cellulose covering and forming one of the chief constituents of plankton; they include bioluminescent forms and forms that produce red tide. They are tiny algae like sea creatures, that can show a surprising dazzle of light when a predator is noticed, and in different ways

diplomacy.noun
the art of maintaining affable relations; skill in dealing with people; tact; the skillful conducting of relations between nations

distil, distiled, distiling,distiling, distils, distils.transitive verbs
to increase the concentration of, separate, or purify by or as if by distillation; to subject (a substance) to distillation; to separate (a distillate) by distillation; to separate or extract the essential elements of (distill the crucial points of the book)
intransitive use.to undergo or be produced by distillation; to fall or exude in drops or small quantities
distillable.adjective

ditzy.or.ditsy, ditzier.or.ditsier, ditziest.or.ditsiest.adjectives
eccentrically scatterbrained or inane

denomination.noun
a large group of religious congregations united under a common faith and name and organized under a single administrative and legal hierarchy; one of a series of kinds, values, or sizes, as in a system of currency or weights (cash registers have compartments for bills of different denominations; the stamps come in 25¢ and 45¢ denominations); a name or designation, especially for a class or group
denominational.adjective
denominationally.adverb

dimwit.noun
a stupid person
dimwitted.adjective
dimwittedly.adverb
dimwittedness.noun

diaphragm.noun
a muscular membranous partition separating the abdominal and thoracic cavities and functioning in respiration, also called midriff; a membranous part that divides or separates; a thin disk, especially in a microphone or telephone receiver, that vibrates in response to sound waves to produce electric signals, or that vibrates in response to electric signals to produce sound waves; a contraceptive device consisting of a thin flexible disk, usually made of rubber, that is designed to cover the uterine cervix to prevent the entry of sperm during sexual intercourse
diaphragmatic.adjective
diaphragmatically.adverb

diabolical.also.diabolic.adjective
of, concerning, or characteristic of the devil; satanic; appropriate to a devil, especially in degree of wickedness or cruelty
diabolically.adverb
diabolicalness.noun

dweeb.noun
a subservient person; a flunky; a despised person

disturb, disturbed, disturbing, disturbs.transitive verbs
to break up or destroy the tranquility or settled state of ("subterranean fires and deep unrest disturb the whole area" ...Rachel Carson); to trouble emotionally or mentally; upset; to interfere with; interrupt (noise that disturbed my sleep); to intrude on; inconvenience (constant calls disturbed her work); to put out of order; disarrange
disturber.noun
disturbingly.adverb

disturbance.noun
the act of disturbing; the condition of being disturbed