圣 is a bound morpheme (b.f.) that appears as the first or second element in compounds. Its core meanings cluster around three domains: religious/moral sanctity (holy, sacred, saint), exceptional human virtue (sage, genius), and imperial authority (emperor, imperial). You'll encounter it in words like 神圣 (shénshèng, holy), 圣人 (shèngrén, sage), and 圣诞 (shèngdàn, Christmas). Because it is a bound form, it never stands alone as an independent word in modern Chinese.