格外【géwài】

格外 says something is more so than it normally is, and the sentence usually gives the reason: after rain, at a festival, on a first time. It's neutral to written, and common in descriptive writing.

It also goes before verbs of feeling or care.

格外 or 尤其

格外 compares a thing with its own usual state. 尤其 and 特别是 pick one item out of a group. So 格外 can't introduce an example.

• × 我喜欢水果，格外是苹果 → 我喜欢水果，尤其是苹果

Not with another degree word

格外 already says the degree, so 很 and 非常 don't go with it.

• × 他格外很高兴 → 他格外高兴