A call option, often simply labeled a "call", is a contract, between the buyer and the seller of the call option, to exchange a security at a set price.[1] The buyer of the call option has the right, but not the obligation, to buy an agreed quantity of a particular commodity or financial instrument (the underlying) from the seller of the option at a certain time (the expiration date) for a certain price (the strike price). 

“call option”一般可以译为：

1.看涨期权

看涨期权就是指赋予持有人在一个特定时期以某一固定价格购进一种资产(既股票,外汇,商品,利率等)的权利。股票看涨期权的价值取决于到期日标的股票的价值。如果到期日的股票价格价高于执行价格，那么看涨期权处于实值，持有者会执行期权，获得收益；如果到期日的股票价格低于执行价格，那么看涨期权处于虚值，持有者不会执行期权，此时看涨期权的价值就是0。

2.购买选择权

具体翻译时应视上下文情况而定。如有明确提及期权的，可以译为“看涨期权”，否则可译为“购买选择权”，如出现在下文这一可转债认购协议中时，毫无疑问译为“购买选择权”更为合适：

9.1Subject to the conditions specified herein, the Issuer may redeem the Convertible Bond, in whole or in part, from the Bond Purchaser (the " Call Option").

根据本协议规定的条件，发行人可向债券买方赎回全部或部分可转换债券（“购买选择权”）。

9.2Exercise of the Call Option shall be notified by the Issuer in writing to the Bond Purchaser at least thirty (30) calendar days prior to the settlement date of 止 e Call Option.

根据本协议规定的条件，发行人可向债券买方赎回全部或部分可转换债券（“购买选择权”）。

9.3On the settlement date of the Call Option, the Issuer shall ay to each of the Bond Purchaser holding the Convertible Bond to be redeemed, m respect of each such Convertible Bond, 小e principal plus eight percent (8%) per annum interest accrued until 小e settlement date.

在购买选择权结算日，发行人应就各份待赎回的可转换债券，向持有待赎回可转换债券的债券买方支付本金加上截至结算日按百分之八（8%）的年利率计收的应计利息。

9.4The Issuer has tl1e right, but not the obligation, to exercise the Call Option any time between one (1) month after the date of tile issuance of the Convertible Bond and one

(1)month before the due date of the Convertible Bond.

发行人有权但无义务在自可转换债券发行日后一（1）个月起至可转换债券到期日前一（1）个月止期间的任何时间行使购买选择权。

“put option”则亦是如此，可根据语境译为“看跌期权”或“卖出选择权”。