換句話說grammar point · tier 1 · reformulation 換句話說 (in other words / to put it another way)
Restates the fact just given in different wording: the same point, said another way.
字源 FORM what the parts do
A hand (扌) takes one thing and sets down another — 換, to swap, 奐 for the sound. 句話 is the sentence just spoken, hooked off into its length (勹 round a 口) and voiced (言). 說 lays the words open again (言 beside 兌 for sound). The four read straight: swap the sentence, say it over. The fact stays; only its wording changes hands.
故事 STORY a scene to remember it by
A hand lifts one wrapping off a thing and sets a different wrapping round the same thing; what is inside never moves.
字源記憶法
框 · Frame
[statement]，換句話說，[same fact, reworded]
觸 · Trigger
You have stated a fact and want to say the very same fact again in different words, so it lands more plainly.
序 · The move
1state the first clause in fullis there a fact already on the table to be reworded?
2open the second clause with 換句話說 (the four-character phrase intact)are all four characters in order, none dropped or swapped?
3say the same fact again in different wordingis the second clause the SAME fact reworded, not a new fact and not a separate consequence?
例 · Examples
1出生率birth rate降低to drop, fall了marks the new state (it has now dropped)，換句話說in other words / to put it another way，就是amounts to, that is孩子children越來越more and more少了。
The birth rate has dropped; in other words, there are fewer and fewer children.
換句話說 trades only the wording: same content, new phrasing, nothing spelled out beyond it. 就是說 draws out the upshot or plain equivalent and can carry the consequence forward. One re-wraps the same fact; the other tells you what it amounts to.
也就是
也就是 equates two terms inside one clause (X，也就是 Y — X, namely Y). 換句話說 reformulates a whole clause into another whole clause. Naming a thing against re-saying a statement.
introducing a new fact instead of a rewording: 出生率降低了，換句話說，我們該多蓋學校 → 出生率降低了，換句話說，孩子越來越少了
breaking the fixed phrase: 換個話說 / 換句說話 → 換句話說
using it for cause→effect with two separate facts: 下雨了，換句話說地很濕 → 下雨了，所以地很濕
English 'in other words / to put it another way' drops in freely, and learners pull the four characters apart or reorder them (換個話說, 換句說話) instead of keeping 換句話說 fixed; they also stretch it to 'and so / therefore' where two distinct facts call for 所以。