Rejected and dejected 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 suggests what word you may want to save time, but quite often, its suggestions couldn’t be more off base and produces humorous results.
Dejected is an adjective in the past tense. It means to feel sad or down.
Rejected is a adjective in the past tense. It describes the person or thing that was refused, dumped, or let go, or the action of rejecting that person or thing.
The following story uses both words correctly:
Reginald felt dejected. He had rejected his partner’s proposal and quit his job, he didn’t know what was next, and he couldn’t talk to his usual friends about it, they all thought his recent choices were crazy. Maybe he would just expatriate to somewhere new.