Callus and callous 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.
Callus (pronounced “kal-us”) is a noun. It means skin that is hardened or thickened as a result of repetitive work with hands. Callus’ can occur from sewing, picking bushels of crops, or working with handtools, just to name a few.
Callous (pronounced “kal-us”) is an adjective. It means to be dispassionate, unsympathetic, and unphased to the pains and crises of other people.
The following story uses both words correctly:
Callista was accused of being callous towards her warehouse workers. They complained of aching backs and callused hands. They were hustling more than usual to fulfill Christmas orders for her business.