Words are often misspelled when they contain a letter that is not pronounced - the silent p in psychology and its 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 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.