115 种时态
----------------
How Many Tenses are There?
Tenses are grouped in families. The present tense, past tense, future tense, and conditional tense are the simple (or basic or potential) family. The progressive family includes the present progressive (am, are, or is eating), past progressive (was or were eating), future progressive (will or shall be eating), and the conditional progressive (could, would, must, might, may, or can be running).
Each family has four members. To save space only the first person present plural members are shown here.
The Four Tense Families in the Present Family Tense Active Passive
Simple Present simple We meet We are met
Progressive Pres. Progressive We are meeting We are being met
Perfect Pres. Perfect We have met We have been met
Perfect Progressive Pres. Perf. Prog. We have been meeting We have been being met
We can do the same for the other three tenses: past, future, and conditional.
Using all the auxiliary and/or "helping" verbs, which I prefer to call "helping parts," one can list 115 tense forms of any transitive verb. Of course, transitive verbs, having no passive voice, have only half as many.
Granted, some of those passive progressive forms are seldom, if ever used, but isn't this a more practical way to consider English verbs?
参考资料：http://englishplus.com/news/news0100.htm