1. BASIC SUBJECT-VERB AGREEMENT

2. Singular sub. + Singular v.
THE BASIC PRINCIPLE
The basic principle behind subject-verb agreement is that a singular subject needs a singular verb whereas a plural subject needs a plural verb.
Singular sub. + Singular v.
Pl. sub + Pl. v.

3. =
Person Number
SUBJECT
VERB

4. SINGULAR VERB PLURAL VERB My friend lives in Boston.
My friends live in Boston.
Verb + -s/-es = 3rd person singular in the simple present tense.
noun + -s/-es = plural

5. Two or more subjects connected by and require a plural verb.
My brother and sister live in Boston.
My brother, sister, and cousin live in Boston.

6. EXCEPTION: EVERY AND EACH
Every man, woman, and child needs love.
Each book and magazine is listed in the card catalogue.
Every and each are always followed by singular nouns.
When there are two or more nouns connected with and the verb is singular

7. Interrupting structures do not affect basic subject-verb agreement
SINGULAR VERB
PLURAL VERB
That book on political parties is interesting.
The book I bought at the bookstore was expensive
The ideas in That book are interesting.
The books I bought at the bookstore were expensive

8. A singular Verb is required.
Gerund
Subject
A singular Verb is required.
Growing flowers is her hobby.