晨 is a bound form (b.f.) meaning 'morning'. Unlike the standalone word 早上 (zǎoshang), 晨 cannot be used alone — it must appear in compound words such as 早晨 (zǎochén, early morning), 清晨 (qīngchén, early morning/dawn), 晨光 (chénguāng, morning light), or 晨练 (chénliàn, morning exercise). When you learn 晨, focus on memorizing it as part of these compounds rather than trying to use it as an independent noun.