诚然【chéngrán】

诚然 grants a point – "it is true that" – before the writer turns with 但(是), 然而 or 可是 to the point they want to make. It belongs to written argument: essays, editorials, speeches.

At the front or after the subject

Most often 诚然 opens the sentence, set off by a comma. It can also stand after the subject like any other adverb.

诚然 or 固然

Both concede and then turn. 固然 must sit after the subject and is common in speech as well as writing. 诚然 is written only, and it can start the sentence on its own, which 固然 can't.

• × 固然，这个计划有问题 → 诚然，这个计划有问题 / 这个计划固然有问题

The turn has to follow

In an argument, 诚然 sets up a "but". A sentence that concedes with 诚然 and never turns reads as unfinished. The longer 诚然…然而 frame has its own point.

• × 诚然，失败是痛苦的。 → 诚然，失败是痛苦的，但我们可以从中学到很多。