Course paper on theoretical grammar

What is a verb? Let’s start with the basics: What is a verb? Verbs are words that describe actions, whether physical or mental. Verbs also describe a “state of being,” like the verbs be, become, or exist. 

Salah ran across the field, kicked the ball, and scored a goal. 
“I am the State.” —King Louis XIV
Some verbs also act as “helper verbs” to change the tense of another verb. Likewise, these helper verbs can change a positive statement to a negative one with words like “not.” 
She has been jogging for a month and already feels her stamina increasing. 
“I don’t feel so good.” —Spider-Man
Every sentence needs at least one verb. If there’s no verb, it’s an incomplete sentence or a sentence fragment. Except for imperative sentences (commands), a sentence also needs a subject, the thing doing the action. Subjects are important for a verb because they change how it’s conjugated, which we explain below. This is especially true for the most common verb: be.