并列结构「既…又/时而…时而」jì…yòu / shí'ér…shí'ér

Coexistence vs. Alternation: 既…又… / 时而…时而… / 一会儿…一会儿…

Meaning: Both A and B (既…又…) / At times A, at times B (时而…时而… / 一会儿…一会儿…)

Pattern

HSK 7-9 requires mastering the stylistic and semantic distinctions among parallel correlative structures:
(1) "既 A 又 B" (both A and B): indicates two qualities or states coexisting simultaneously with the same evaluative polarity (both positive or both negative, e.g., 既聪明又勤奋).
It is more formal than "又 A 又 B".
(2) "时而 A, 时而 B" (at times A, at times B): literary pattern describing two states alternating over time, commonly used in depicting weather, scenery, or moods (e.g., 时而晴朗，时而阴雨).

1
他既聪明又勤奋,深受老师喜爱。
Tā jì cōngmíng yòu qínfèn, shēn shòu lǎoshī xǐ'ài.
He is both intelligent and diligent, and is deeply loved by his teachers.
2
天气时而晴朗,时而阴雨,变化无常。
Tiānqì shí'ér qínglǎng, shí'ér yīnyǔ, biànhuà wúcháng.
The weather is sunny at times and overcast and rainy at others, changing unpredictably.
3
孩子一会儿哭,一会儿笑,情绪不稳定。
Háizi yīhuǐr kū, yīhuǐr xiào, qíngxù bù wěndìng.
The child cries one moment and laughs the next; his emotions are unstable.

•既…又… indicates simultaneous coexistence of qualities; 时而…时而… (literary) and 一会儿…一会儿… (colloquial) indicate temporal alternation.

⚠️ Common Mistakes:

•Confusing 既…又… (simultaneous coexistence) with 时而…时而… (mutually exclusive states alternating over time, like sunny vs. rainy).

•Pairing two opposite-polarity adjectives in 既…又… (e.g., one positive and one negative—use 虽然…但是… instead).

•Placing the subject after 既 (*既他聪明又勤奋 -> 他既聪明又勤奋 when sharing the same subject).

•Confusing 一边…一边… (two actions done at the exact same moment) with 一会儿…一会儿…

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