似乎 (sìhū) is a formal, written adverb meaning 'it seems, seemingly' — it expresses a tentative impression or inference. It's more literary than 好像 (hǎoxiàng), which is the everyday spoken word for 'seems like' and can also mean 'as if'. 仿佛 (fǎngfú) is similar in register but often implies a stronger sense of resemblance or vividness.