The base form of verb is called-

To+verb এর base form(present form)  এর পূর্বে to বসে infinitive গঠিত হয়।
-  A weak verb is not the same as a regular verb, which is a verb that complies with the normal rules forming its various forms.
- A weak verb is one that ends ''-d'' or ''-t'' for its past forms (i.e., its simple past tense and past participle).
- Example: curse (present), cursed (past), cursed (past participle),
- sell (present), sold, (past), sold (past participle),
- dream (present), dreamt (past), dreamt (past participle)

Source:Advanced Learner's Grammar and Composition by Chowdhury and Hossain