adjective
1
BAD : I feel quite confident with my English.
GOOD : I feel quite confident about my English.
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confident about sth : 'The more familiar you are with the machine, the more confident you will be about using it.'
2
BAD : I began to feel more confident of myself.
GOOD : I began to feel more self-confident.
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If you have confidence in your own abilities, you feel self-confident : 'Even as a child he was surprisingly self-confident and didn't mind being left with strangers.