相对而言【xiāngduì ér yán】

相对而言 says a judgement holds in comparison with other options or with what is usual, not in absolute terms: "relatively speaking", "comparatively". It goes before the judgement – at the head of the sentence with a comma, or after the subject – and the predicate usually carries 比较, 更 or 一些 to show the degree is relative. It is neutral to written.

When two or more things have just been named, 相对而言 picks the one that comes out ahead.

相对而言 or 相比之下

相比之下 needs a specific thing just described to compare against: A is like this; by comparison, B is like that. 相对而言 can compare with an unspoken norm, so it can open a sentence with nothing before it.

Before the judgement, not tagged on

English can add "relatively speaking" at the end. In Chinese it comes before the judgement.

• × 这里很安静，相对而言 → 相对而言，这里比较安静

相对 on its own before an adjective, as in 相对便宜 "relatively cheap", does the same job inside a phrase.