When unsure how a word is spelled, the best resource, of course, is a dictionary. But without one on hand, I often ‘sound out’ the word using the phonetics I learned in grade school. Here’s where I run into trouble with prescription, because I mispronounce it! Many Americans also say the word as if the prefix were per-, but prescription is correct.
To make matters worse, my second desperate technique–guessing at the word origins–also fails me. My reasoning goes something like this: “per-scribe, okay that probably means as-written so per- must be correct. Pre-scribe might mean before-written and that makes less sense.” Again, I’m wrong. Merriam Webster gives the following origin for prescription:
When I’m tempted to skip the dictionary because a word seems correct, prescription reminds me of the risk I’m taking. If you mispronounce the word, try to change that! (This is not easily done–I learned I was mispronouncing spinach twenty years ago and still don’t nailed it every time.)