同样 (tóng yàng) is an adjective meaning 'same' or 'equal', often used before a noun or as an adverb ('equally'). It's more formal than 一样 (yī yàng), which is the everyday word for 'the same' and also used in comparisons ('A 跟 B 一样'). 相同 (xiāng tóng) is a written, abstract 'identical' (e.g., results, opinions).