The bare infinitive is the form of the verb without "to".
The bare infinitive is used:
- as the main verb after the auxiliary verb do, or most modal auxiliary verbs (will, can, etc.): "I will go" (
I will to go);
- after had better: "You had better ask him";
- with the verb help: "She helped him finish it";
- with why: "Why do it later?".