A2
係…嘅 — it was “then”, it was “there”
How the 係…嘅 pattern puts the spotlight on when, where or how something happened in Cantonese, and why 我琴日嚟咗 and 我係琴日嚟嘅 are different sentences.
係…嘅 is used when you both already know the event happened and the question is one of its details — when, where, how, with whom.
你係幾時嚟嘅？
Nei5 hai6 gei2si4 lai4 ge3?
When did you get here?
我係琴日嚟嘅。
Ngo5 hai6 kam4jat6 lai4 ge3.
I got here yesterday.
你係咪坐飛機嚟㗎？
Nei5 hai6 mai6 co5 fei1gei1 lai4 gaa3?
Did you fly here?
係咪 there is the contracted A-not-A of 係 — 係唔係 said quickly — and it is what you will hear far more often than the full form.
Against 咗
Both of these are correct and they are not interchangeable.
我琴日嚟咗。
Ngo5 kam4jat6 lai4zo2.
I came yesterday.
我係琴日嚟嘅。
Ngo5 hai6 kam4jat6 lai4 ge3.
It was yesterday that I came.
The first reports that the coming happened. The second assumes you knew that and tells you which day. If someone can see you standing in front of them, asking 你幾時嚟咗 is odd and 你係幾時嚟嘅 is the natural question.
嘅 often becomes 㗎
嘅 plus 呀 fuses into 㗎, so the spoken form of this pattern very often ends 㗎 rather than 嘅 — 你係幾時嚟㗎? Same construction, one syllable.
The negative keeps 係
唔係…嘅, and this is the one place 係 cannot be dropped.
我唔係琴日嚟嘅。
Ngo5 m4 hai6 kam4jat6 lai4 ge3.
It wasn’t yesterday that I came.
唔係 rather than 冇 — you are not denying that the coming happened, only correcting a detail of it, which is the whole point of the pattern showing up in one word.