影 is a bound morpheme (b.f.) — it cannot be used as a standalone word in modern Mandarin except in a few set phrases (e.g., 如影随形) or poetic contexts. It appears in many common compounds covering the senses of 'shadow' (影子), 'reflection' (倒影), 'image, photography' (影像, 摄影), 'movie, film' (电影, 影星), and 'influence' (影响). The verb sense 'to hide, conceal' occurs in compounds like 隐影 but is less frequent. Understanding the bound status helps you avoid using 影 alone.