In a sentence, subject and verb must agree , for example, if subject is singular then verb must be singular, for instance, India is a country, here, India a singular noun and the verb used is "is" so here, there is agreement between subject and the verb. Other examples are Boys are running on the road. [ Boys (Plural Subject) Are ( Plural Verb)] Below there is not agreement between subject and verb. Girls is studying in the class room. The above examples were very simple, here I will explain the students, bloggers make mistakes whenever subject is little bit confusing. Compound Subject - Some nouns come in pair and make a compound singular subject and they require a singular verb. Examples are - Slow and steady wins the race. Bread and milk is my favorite breakfast. Rice and curry is the delicious. Pen and ink is used to write on the paper. But many compound are treated as plural and they require plural verb. Examples are -