should I be free

上面的句子 = If I should be free, I will come。这种条件从句(包括真实条件从句与虚拟条件从句)可以通过主谓倒装来取消连接词,不妨称作无连词条件从句。根据现代语言学家的观点,这种句型大都用于多少带有一些文学色彩的语体中:

1. Should she be interested, I'll phone her. 要是她感兴趣的话，我就打电话给她。

2. Should you change your mind, no one would blame you. (CGEL) 要是你改变主意的话，谁也不会责怪你。

3. Should you be interested, I'll tell you the whole story. 要是你感兴趣的话,我就把这事原原本本告诉你。

除了 should 之外, had, were 也可以用在无连词条件从句中(见 had he been, were $^{1-3}$ )。