D

dash, hyphen

• See Punctuation.

data, datum

• Data is singular when it is used as a collective noun that represents a unit. This data is not logical.
• Data is plural when it refers to individual items: The data are in line with the previous research.
• Use datum in reference to a single bit of information.

databank, database

data center, data processing (n. and adj.)

data set

dates

• Use the sequence of month, day and then year, placing a comma after the day of the month: School starts on September 2, 2012.
• If the day of the month is not provided, do not use commas: He received the award in December 2004.
• Days of the week should precede the date and should be followed by a comma: He died on Tuesday, October 10, 2000.
• Avoid superscript constructions such as January 15th. Write as January 15. Use superscript constructions only in reference to centuries: He lived in the 19th century.
• Also see months.

daycare

• One word.

day to day, day-to-day

• Hyphenate when used as a compound modifier: They have extended the contract on a day-to-day basis.

daylight saving time

• Not savings. No hyphen.

daylong

days of the week

• Do not abbreviate days of the week in running text.
• In tabular format where space is limited, abbreviate the days as follows, without periods: Sun, Mon, Tue, Wed, Thu, Fri, Sat.

daytime

dean

• Capitalize when used as a formal title before a name: Dean Sherif Kamel; otherwise, lowercase.

dean’s list

• Lowercase in all uses

decades

• Add the letter s with no apostrophe: the 1990s, or use an apostrophe and write as: the ’90s. The important thing is to be consistent.
• Always precede decades with the word the.

decision making

• Two words, no hyphen. But hyphenate when used as a compound modifier: decision-making process.

degrees

• See academic degrees.

degrees with distinction

• Lowercase cum laude (honors), magna cum laude (high honors), summa cum laude (highest honors). Do not italicize.

delegate

• Lowercase: She served as a delegate at the Model United Nations.

departments

• Click here for a list of academic departments.

-designate

• Hyphenate: dean-designate. Capitalize only the first word if used as a formal title before a name.

dialogue

• Not dialog (also dialoguing, dialogued).

dimensions

• Use figures and spell out centimeters, meters, inches, feet, yards to indicate height, length and width: 6 centimeters, 1 meter, 4 yards.
• Always use figures and hyphenate adjectival forms before nouns: He climbed the 4-meter long ladder.

 diplomas

• You have a diploma in (not of) a certain field: diploma in teaching. Use of if it is part of the official name: Diploma of Higher Education.

directions

• Lowercase when referring to a compass direction: Take the highway north.
• Capitalize when referring to specific regions: the Far East, the North Coast, the Midwest, the Western Hemisphere or names of countries: Northern Ireland, South Korea.
• Lowercase when directions describe a section of a state or country: western Texas, southern California.

disinterested, uninterested

• Disinterested means impartial, neutral, not taking sides: disinterested party in the dispute; disinterested referee. Uninterested means that someone lacks interest: He was uninterested in the subject.

disk, disc 

• Use disc to refer to phonograph records, disc jockey and laser-based devices (laserdisc, videodisc, and a blu-ray disc), as well as for disc brake.
• Use disk to refer to the hard disk on which computer data can be stored and for medical references, such as a slipped disk.

diaspora

• Dispersion of people away from their homeland. Lowercase. 

distinguished visiting professors

• Capitalize when preceding a name: Distinguished Visiting Professor Maria Menocaul spoke about the art and architecture of Medieval Spain.
• Lowercase when it comes after the name: Maria Menocaul, distinguished visiting professor of Spanish and Portuguese at Yale University, gave a lecture yesterday.
• Also lowercase when not associated with a name: He is a distinguished visiting professor of chemistry.
• Use DVP on second reference.

do's and don'ts

doctoral, doctorate, PhD

• Doctoral is used as an adjective: He is a doctoral candidate at the University of California, Santa Barbara. He entered the doctoral program last year.
• Doctorate or PhD is the degree that someone earns: She earned her doctorate after five years of hard work.
• Capitalize honorary degrees: honorary Doctorate of Science, honorary Doctorate of Humane Letters. See honorary degrees.

dollar

• Put the $ sign before the figure, leaving no space: He earns $50 per week. Do not use $ before the amount and the word dollars after it.
• Spell out as dollars lowercase when no figure is given: I lent her a dollar. His bank account is in dollars.
• When the figure is in millions, spell out the word million and use numerals up to two decimal places: He won $5.75 million.
• For specified amounts, the word takes a singular verb: The ransom they requested was $250,000.

door to door, door-to-door

• Hyphenate when used as a compound modifier: He is a door-to-door salesman. But: He went from door to door.

Dr.

• Use for medical doctors or dentists, not people with doctorate degrees.
• Capitalize and use before the name: Dr. Magdi Yacoub performed sensitive heart surgery.

drive-through

dorm, dormitory

• Capitalize Zamalek Dormitory, as it is the official name. Use hostel on second reference.
• Could also refer to it as the dormitory, the AUC hostel or the Zamalek residence.
• Avoid dorm (casual reference).

double-click

double-faced

down-

• The rules for prefixes apply, but in general, no hyphen. Some examples: downgrade, downtown, download. 

down payment

drop/add

• Do not capitalize. Separate with a slash, not a hyphen.
• Do not use add/drop.

drop out (v.), dropout (n.)

DVD

• Abbreviation on first reference for digital video disc (or digital versatile disc).

DVR

• Acceptable on second reference for digital video recorder.