Person And Number - Verbs & Verbals - Parts Of Speech-ESL/Learn English Grammar

PERSON AND NUMBER.

235. The English verb has never had full inflections for number and
person, as the classical languages have.

When the older pronoun _thou_ was in use, there was a form of the verb to correspond to it, or agree with it, as, 
"Thou walk_est_," present;
"Thou walked_st_," past; 
also, in the third person singular, a form ending in -_eth_, as, 
"It is not in man that walk_eth_, to direct his steps."

But in ordinary English of the present day there is practically only
one ending for person and number. This is the third person, singular
number; as, "He walk_s_;" and this only in the present tense
indicative. This is important in questions of agreement when we come to syntax.