The requirements for the language on slides are:

1. Brevity,
2. Correct spelling and grammar,
3. Canadian/British English versus American English, and
4. Other suggestions.

5.2.4.1 Brevity

As noted, the audience is able to read 5-10 times faster than the speaker can talk and consequently, and as vision is the primary means of acquiring information, any text on a slide will quickly and occupy the attention of the audience. The text on a slide must be brief for two reasons:

• The audience should not spend inordinate amounts of time reading slides, and
• The slides must not replace the speaker.

Each time the author has critiqued a student's slides, the single most significant problem has been the amount of text on the slides. With each phrase, adverb, or adjective, ask whether that text assists the audience to better understand the objective of the presentation.

5.2.4.2 Correct Spelling and Grammar

Correct spelling and grammar is essential to a good technical presentation. The audience will note spelling errors and each spelling error will take 2-5 seconds of attention away from the speaker. With modern spelling and grammar checkers, there is no excuse for such errors and a plethora of such errors will make the speaker appear to have no regard for the audience and little interest in the presentation. Poor spelling can sometimes result in significantly greater fame than the presenter initially anticipated, as is demonstrated in Figure 1.

Figure 1. Spelling errors with international fame.

While spelling errors can be quickly caught by a spell checker, there are words which are phonetically close or identical (homonyms) but with significantly different meanings. Some of these are listed here:

accept  except
affect  effect
advise  advise
its  it's
their  there  they're
to  too  two
your  you're

Very useful on-line sources are:

• Bob the Angry Flower:
  • Bob's Quick Guide to the Apostrophe, and
  • Destroy the Apostrophe;
• the Purdue On-line Writing Lab; and
• Common Errors in English Usage.

5.2.4.3 Canadian/British English versus American English

The spelling of a technical presentation must be tailored to the audience. Regardless of one's home country or personal preference, the speaker should follow the accepted usage of the intended audience. These guidelines are written using Canadian English however an American audience will view Canadian spellings as pretentious and Canadians will view American spellings as, well, American. For example, as soon as the word "colour" appears in a slide in a presentation given to a mostly-American audience at an American work place, a significant portion of the audience will, for a second or two, note the difference and in that time ignore the speaker.

5.2.4.4 Other Suggestions

Other suggestions to remember are:

• Words on slides should never be broken across multiple lines through hyphenation;
• All foreign words and abbreviations/initialisms of foreign words must be italicized, e.g. ad hoc;
• Use quotes only when making direct quotes or when (less common in technical presentations) implying sarcasm;
• Use hyphens for compound adjectives:
  • a dark green car is a green car which has little light shining on it while a dark-green car is a car which a deeper shade of green, and
  • 32-bit processors represents an undefined number of processors with 32-bit addresses while 32 bit processors represents thirty-two objects called bit processors, and
  • This is a far-too-long list;
• When listing lists within lists (like this one), the items in the outer list should be separated with semicolons; and
• Define unfamiliar abbreviations, initialisms, or acronyms (AIA) the first time they are used and use the AIA thereafter; however, the presentation should not turn into a quagmire of TLAs.