擅 almost always appears in compounds: 擅长 (shàncháng, be good at), 擅自 (shànzì, without authorization). On its own it's literary. 擅长 is slightly more formal than 会 or 很会.
mistakes
Don't confuse 擅长 (good at) with 善良 (shànliáng, kind-hearted). Different first character, different meaning entirely.