de reduce, away, down, remove decelerate – to slow down, reduce speed; dethrone – to remove from power; debug – to remove bugs

dec/a, deka ten decade – 10 years; decathlon – athletic contest that includes 10 disciplines in which each participant competes; December – formerly the 10th month of the Roman calendar

deci one tenth deciliter – a tenth of a liter; decimate – reduce dramatically; decibel – one tenth of the sound volume unit bel

dem/o people democracy – government of the people; demographic – the study of people; epidemic – spreading among people in a region

demi half, less than demitasse – a small cup of coffee; demimonde – someone of little respected life style

dendr/o/i tree philodendron – a climbing plant that grows on trees; dendrochronology – dating events by studying growth rings in trees; dendriform – in the shape of a tree

dent, dont tooth dental – relating to teeth; dentist – a doctor for the teeth; dentures – a set of false teeth

derm/a skin dermatologist – a doctor for the skin; pachyderm – a class of animals with very thick skin (elephant, rhinoceros); dermatitis – inflammation of the skin

di/plo two, twice dichromatic – displaying two colors; diploma – a certificate, literally “a letter folded double”; dilemma – a situation that requires a choice between two alternatives.

di/s apart, away, not, to the opposite digression – a departure from the main issue, subject; disappear – to move out of sight; dissect – to cut apart piece by piece.

dia through, between, apart, across diabetes – disease characterized by excessive thirst and discharge of urine; diagnosis – understanding a condition by going through a detailed review of symptoms; dialog – conversation between two people.

dict speak contradict – to express the opposite of; prediction – a statement foretelling the future; dictate – to speak out loud for another person to write down.

domin master dominate – to be the master of; domineering – excessively controlling; predominate – to have more power than others

don/at give donation – a contribution or gift; donor – someone who gives something; pardon – to give forgiveness for an offense

duc/t lead conduct – to lead musicians in playing music; educate – to lead to knowledge; deduction – a subtraction of an amount.

du/o two, twice duplicate – make an identical copy; duet – a musical composition for two voices or instruments; duo – a pair normally thought of as being together.

dur harden, to last, lasting durable – having the quality of lasting; duration – the length of time something lasts; enduring – able to last.

dyn/a/am power, energy, strength dynamo – a generator of energy; dynamic – having physical energy/power; dynamite – a powerful explosive.

dys abnormal, bad dyspepsia – abnormal indigestion; dystopia – an imaginary place of total misery; dyslexia – impairment of the ability to handle words.