allô
hello (used when answering or checking on a phone call)
is anyone there? (used on the phone to check the connection)
hey / hello (used figuratively to express surprise, disbelief or to call someone's attention — like 'are you serious?')
Mais allô ! T'as 20 ans et t'as pas de shampoing ?
I mean, seriously! You're 20 and you don't even have shampoo?
Notes
GENERAL INFO
Allô is an interjection. It primarily means "hello" when answering or making a phone call, or "hello?" to attract someone's attention if they seem unaware or distracted.
USAGE
You use allô to initiate or respond during a phone conversation: "Allô? C'est qui?" (Hello? Who is this?). It can also be used to get someone's attention: "Allô! Tu m'écoutes?" (Hello! Are you listening to me?).
TRAPS
Do NOT use allô for a general greeting like "Bonjour." It's exclusively for phone calls or when trying to get someone's attention, not for meeting someone in person.
