grammar → 既…又…
TSUMUGU · TBCL 4 (est.) · 語法
既…又… grammar point · tier 2 · 既…又… a matched pair of qualities, both holding of one subject
Pairs two qualities of one subject, the second resting on the same footing the first sets — a balanced, matched pair held together.

字源 FORM what the parts do

既 is a heaped food bowl (皀) with a person turned from it, full (旡) — the meal already over, so 既 sets down the first quality as a settled given. 又 is the bare right-hand graph, its hand-senses gone to 右 and 有, kept here for 'also' — it lays the second quality alongside on the same footing. The same subject runs through both brackets.

故事 STORY a scene to remember it by

One thing on the table wears its first mark as settled; a second mark of the same weight is set beside it, the pair sitting level.
字源自撰記憶法
框 · Frame
[subj] 既 [A] 又 [B]
觸 · Trigger
You want to pin two qualities of one subject as a balanced, matched pair, the second carrying the same weight as the first.
序 · The move
1name the one subject both marks land on
2既 + first quality Ais A a state or quality, not a one-off action — and set down as given?
3又 + second quality Bdoes B sit level with A — same footing, same direction, not a step up or a turn against it?
例 · Examples
1這家this (measure 家 for shops)賣的that (it) sells水果fruit新鮮fresh好吃tasty, good to eat
The fruit this shop sells is both fresh and tasty.
界 · Boundary
又…又…
既…又… is the formal, written twin and leans the two qualities as a matched pair; 又…又… is the plain colloquial version. 既 cannot open with 又 (既…既… is wrong), and 既 leads — the 既 quality is the given one, the 又 quality the added one.
不但…而且…
既…又… lays two equal qualities flat, neither outranking the other; 不但…而且… steps up — the second claim goes further than the first.
雖然…但是…
既…又… runs the same direction — both qualities agree; 雖然…但是… reverses — the second turns against what the first set up.
repeating the same marker: 既新鮮既好吃 → 既新鮮又好吃
joining the qualities with 和: 既新鮮和好吃 → 既新鮮又好吃
putting a one-off completed action under it: 既吃了飯又看了電影 → 又吃了飯又看了電影 (or just sequence the actions)
English 'both … and …' uses one conjunction across the pair; learners drop the second marker (既 A, B) or splice the two qualities with 和.
關 · Related
又…又…the colloquial twin — same stacking of two co-present qualities, plainer register and no leading given不但…而且…the uphill cousin — the second claim outranks the first instead of sitting level with it雖然…但是…the reversing cousin — the second clause turns against the first instead of agreeing with it