Words are often misspelled when they contain a letter that is not pronounced - the silent p in psychology and related words is an obvious example. It's easy to leave out these silent letters. Some letters are particularly likely to give trouble:
> C. Many words are spelled with a silent c following s: for example abscess, descend (with descent); omniscient; words ending in -esce, -escent, or -escence, such as acquiesce, effervescent, convalescent. A silent c may also occur before k or q: examples include acknowledge; acquainted; acquire.
> D. Silent d is easy to omit before j, as in adjourn; adjunct; adjudicate; adjust.
> G. G should precede n in words like align; foreign; reign. G is also sometimes followed by a silent u, as in guarantee; guard; beleaguered.
> H. Silent h is particularly common after r - as in diarrhoea (made harder by the double r and the diphthong oe); haemorrhage (a double r adds to the difficulty again); rhythm.C is another letter likely to be followed by h- in saccharine, for example - and remember the h in silhouette.
While thinking about silent letters, remember the t in mortgage and the b in debt and subtle. Watch out as well for the i in parliament.
Some words may have whole syllables that are not pronounced and may be left out in writing. Contemporary is is often pronounced and spelled contempory; itinerary is similar.
Sometimes the omission of a letter or syllable comes from a mistaken pronunciation. Many people fail to pronounce the c in Arctic and Antarctic, and so leave it out when writing the words. The first r in February is often left out in both speech and writing, as is the first r in secretary. Quantitative may be shortened in speech to the more manageable quantitive, and spelled accordingly.