一係 … 一係 yáthaih … yáthaih ‘either … or’ 

Meaning:
“一係 … 一係” is a Cantonese structure used to express “either … or,” indicating a choice between two options. It is commonly used in informal contexts to present two alternatives.

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Structure:

一係 + Option 1, 一係 + Option 2

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Usage:

1. It expresses a contrast between two choices, requiring one to be selected.
2. It is used to describe different actions, attitudes, or situations.

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Examples:

1. Choosing an action:
   • 一係你做，一係我做。
     (Yáthaih nei5 zou6, yáthaih ngo5 zou6.)
     (Either you do it, or I will do it.)
2. Making a suggestion:
   • 一係你今晚去睇戲，一係留喺屋企休息。
     (Yáthaih nei5 gam1maan5 heoi3 tai2 hei3, yáthaih lau4 hai2 uk1 kei2 jau1 sik1.)
     (Either you go watch a movie tonight, or stay home and rest.)
3. Stressing a choice:
   • 一係認真啲做，一係唔好做喇！
     (Yáthaih ying6 zan1 di1 zou6, yáthaih m4 hou2 zou6 laa3!)
     (Either take it seriously, or don’t do it at all!)

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Notes:

1. “一係 … 一係” emphasizes a binary choice, often suggesting that the two options are mutually exclusive.
2. This structure is mainly used in spoken Cantonese and can vary in tone depending on the context, ranging from casual to assertive.

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English Equivalent:

The function of “一係 … 一係” is similar to the English “either … or.” For example:

Either you finish your homework, or you go to bed early.
→ 一係你做晒功課，一係你早啲瞓。