a stock exchange in New York
"The amex saw its trading volume surge as new tech stocks were listed on the board today."
An American Express credit card.
"The flight attendant asked if I wanted to use my amex for the purchase."
In plain English: Amex is short for American Express, which is a well-known company that lets people use credit cards to buy things and pay bills online or at stores.
"She paid for lunch with her Amex card at the restaurant downtown."
Abbreviation of American Express.
"The merchant accepted payment via amex when all other credit cards were declined."
Amex is a clipped compound formed by taking the first syllables from American Express and combining them into a single brand name. The term entered common usage as a convenient shorthand for the credit card company rather than evolving from an older meaning.