Two words, in all cases.

But: Executive Master of Healthcare Leadership (when referencing the program name only)

Spell out on first reference, but subsequent use of the acronym is permitted. Note that an individual person is not a HUG; but a person can be from a HUG. HUG can be used as an adjective:

• There was a slight decrease of HUG medical students in 2015.

Modifying phrases are hyphenated when used before a noun, but not after — unless the hyphen is needed to prevent confusion:

• He was a well-known man.
• He was well known.
• She has a full-time job at Brown.
• She works at Brown full time.

Words formed with prefixes (nonprofit, predate, pre-existing) are only hyphenated to avoid duplicate vowels and consonants.

• anti-inflation
• shell-like
• pre-empt

Two or more hyphenated modifiers having a common base are treated in this way:

• long- and short-term memory
• two-, three- and 10-minute intervals

Do not use a hyphen after words ending in “ly” followed by a participle or adjective:

• poorly attired man
• historically underrepresented group

Use an em dash (—) sparingly to indicate emphasis or explanation, to define a complementary element or to denote a sudden break in thought. Put a space on each side of an em dash.

• The influence of three impressionists — Monet, Sisley and Degas — can be seen in his work as a painter.

Note: On an Apple keyboard, form an em dash by selecting option+shift+hypen. On a PC select Alt+0151.