For lexical verbs, the base form is used for (1) the bare infinitive and (2) the finite conjugations for all present tense lexical verbs except the third person singular, present tense, indicative mood.
It is also the basis for the following derived forms:
- The third person form is created by inflecting third person -s onto the base form.
- The to-infinitive is created by adding the particle "to" before the verb.
- The -ing form is made by inflecting -ing onto the base form.
- For regular lexical verbs, the preterite is made by inflecting -ed onto the base form. However, irregular verbs vary from this.
The main exception is the verb be, which is highly irregular. It has the base form "be", from which can be formed a to infinitive "to be", and an -ing form "being". However, its conjugation is all irregular.
Full modal verbs also have a base forms, i.e. can, may, must, shall, will. They lack -ing forms and infinitives.