Mezanmi! is an interjection uttered when you are surprised, scared or shocked. It is synonymous with oh dear!, Oh my God!, oh no!. It may be used to convey a range of emotions.
Examples:
1. you just found out that a good friend had suddenly died, you are shocked and say, "Mezanmi!"
2. You're walking in the woods and come upon a poisonous snake, you'd say, "Mezanmi!" and just split.
3. Your child just spilled chocolate syrup on your expensive white carpet, you'd say, "Mezanmi!"
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Mezanmi also means, "my friends".
You come up onto a group of people that you know. You could say, "Bonjou mezanmi!" (Hello friends).
If speaking publicly, you could start your speech with, "Mezanmi,..." meaning, (my fellow people,...)
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Ah monchè - is synonymous with 'come on, man!' It conveys a persuasive emotion.