Essay and Assay are easily confused words.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It’s suggesting what word you may want to save time, but quite often, its suggestions are pretty off base. They don’t help you out, but they do make you laugh.
Essay is a noun. It means a short literary composition on a theme. Essays are common exercises in grade school so children learn to string their ideas together. Essay can also mean an attempt, or to run through a test or trial, but these meanings aren’t used very much.
Assay is a verb. It means to scrutinize a situation, an event, or an object. With objects, assaying may involve determining if precious metals exist in an object, or in testing a drug to see what it’s components are.
The following story uses both words correctly:
Esme’s June, July, and August had been action-packed. She didn’t know quite how to condense it, to assay her break, into a proper essay of what she did on her summer vacation.