Correction: 個別股 票一手有不同的股數 ，例如匯豐控股 (0005.HK) 一手為 400 股，長江實業 (0001.HK) 一手為 1,000 股，恆生銀行一手 則為 100 股。低於一手的股數交易 ，稱為碎股交易 ，通常交 易價格會較 整手股 數的市價有所折讓 http://www.honsec.com.hk/HWweb/Content.Files/HongKong.Files/pdf/hkstock.pdf

I may give you another word to consolidate the word you mentioned: shareholder : 股東 (股份所有人)

Addendum: The translation should usually be a "lot" of shares. There's also the "board lot", which is a standardized number of shares defined by a stock exchange as a trading unit. As I said, one lot is often defined as 100 shares. But it can be different, for example on the Hong Kong Stock Exchange, as mentioned above. So always be careful, because lots are defined differently. Check with the stock exchange, or the exchange for whatever security you're doing business with. It would certainly be unfortunate if you buy or sell the wrong number of shares ...

You're right, 股票 is "shares", commonly called "stock" in American English. And 100 shares are 1 手：100股为一手