咪
[粵] /mai5/
(v) don't; shouldn't; mustn't
Example:
咪行住 (don't go yet)
咪郁 (don't move)
咪使旨意 (don't count on it)
Notice: It is read as /mai5/
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咪
[粵] mai6
(1) isn't; wasn't; aren't (used as a syllable blending from m4hai6 唔係)
(2) (often used with 囉) then; as a result; might just as well
(2) Example:
冇麵包咪食蛋糕囉 = If there's no bread, (then/ might just as well) eat cake
有錢咪放人囉 = If there's money for us, then we will let him go
Notice: 咪 in 咪...囉 is read as /mai6/
我已經做晒啲嘢,(咪)返屋企囉!
I've finished all the tasks, (as a result/ might just as well) I go home
'I've finished my tasks already, so I am going home!' is indeed a correct translation
Since it is used with the final particle 囉, the 咪 in this sentence is read as /mai6/, and it means "as a result" or "might just as well" based on the context
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Edit: Might as well add the following
咪/mai6/ (1) Example:
(咪)又係佢? = (唔係)又係佢? = (不是)又是他嗎? = isn't it him again
(咪)一樣? = (唔係)一樣? = (不是)一樣嗎? = isn't it the same?