How many verb words in English language?

It's impossible to count how many verbs there are in English, because people are always inventing new ones. If you counted all the English verbs you could find, your number would be wrong again within a day, because someone would invent a new verb like "twerk".

But if you mean "how many ways can a verb be conjugated in English", the answer is a maximum of five: for example, eat, eats, eating, ate, eaten. The only exception is "to be", which has eight: be, is, am, are, being, was, were, been. Note that this number is different from the number of verb tenses that English has, which in standard English is twelve:

had eaten (past perfect)

had been eating (past perfect progressive)

was eating (past progressive)

ate (preterite, a.k.a. past)

has eaten (present perfect)

has been eating (present perfect progressive)

is eating (present progressive)

eats (present)

will have eaten (future perfect)

will have been eating (future perfect progressive)

will be eating (future progressive)

will eat (future)

(In some dialects there are other tenses too, like in "African-American Vernacular English", a.k.a. Ebonics, which has tenses like "bin ate" (remote past): "she bin ate that hot dog" corresponds to standard English "she ate that hot dog a long time ago".)