Ah, yes. Sadly, terminology has always been a problem.
These are verbs in the base form:
leave
want
excel
pass
Notice how there is no s, ed, or other part attached to the end of the verb.
These are not verbs in the base form:
leaves, left, leaving
wants, wanted, wanting
excels, excelled, excelling
passes, passed, passing
Some teachers use different terms to refer to the infinitive without the to. Some of these terms include:
bare infinitive
root of the verb
verb root
dictionary form
These terms are also acceptable ways to refer to the base form.
Source
Hope that helps.
