$500 billion

That's the approximate amount of market cap lost by Apple since its four-session losing streak started Wednesday. The iPhone maker had just reclaimed its market-cap crown earlier in the week, but it has now slipped back to third among U.S. companies. Here are the top three as of this morning's trading, according to Dow Jones Market Data:

-- Nvidia: $5.01 trillion

-- Alphabet: $4.50 trillion

-- Apple: $4.46 trillion

Apple is the only Magnificent Seven tech stock to be down on the day Monday.