早上 (zǎo shang) refers to the early part of the morning, roughly from sunrise to about 8–9 AM, and is the most common everyday word for 'morning' in spoken Chinese. 上午 (shàng wǔ) is a broader time block covering the entire morning until noon (roughly 6 AM–12 PM), often used for schedules and appointments. 早晨 (zǎo chen) is slightly more formal and literary, while 清晨 (qīng chén) is poetic for 'early dawn'.