Rules for subject verb agreement
1.)When words like the following are used as subjects, they take singular verb. EverybodyAnybodySomebodyNobodyEachEveryoneAnyoneSomeoneNo oneEitherEverythingAnythingSomethingNothingNeither Everybody knows the answer.Nobody speaks German here.Somebody was in the room. When every and each come before a singular subject joined by and, the verb is singular. Every man and woman has the right to vote.Each student and teacher was aware of the difficulty. Prepositional phrases that come between the subject and the verb do not change the number of the subject. The teacher as well as the students was working on the problem.The mother together with her children is waiting. Some examples of prepositional phrases that function like that are:As well asIn addition toTogether withAlong withExcept When the verb comes before the subject as in there or here sentences, it agrees with the subject that immediately follows the verb. There is a tree in the garden.There are many trees in the garden.There is a pine tree and some oaks in the garden. There goes the cat.There seems to be a relationship.There arise problems.There arises a problem. “Introductory it” is always singular. It is my sister who works in the hospital.It is my cats which cause the trouble. Subjects joined by and take a plural verb (except for number
 My sister and brother live in Berlin.Both the teacher and the student were surprised. Several, many, both, few are plural words and take a plural verb. Both are happy with the grades they got.Many were lost on the way.Few have done their homework. Some nouns are always plural and always take a plural verb. Trousers, pants, slacks, shorts, briefs, jeansGlasses, sunglassesScissors, pliers, tweezers My jeans are old.This year shorts are in fashion.Where are my scissors? Some words such as none, any, all, more, most, some, majority, half may take either singular or plural verbs depending on the meaning. All the money has been spent.All of the students know the answer. When subjects are joined by words such as neither, either, not only the verb must agree with the closer subject. Either the man or his wife knows the answer.Either the man or his friends know the answer.Either the children or the man knows the answer. Collective nouns are usually singular when regarded as a unit. My family lives in Ankara.Our team has won every game this year. Sometimes when the members are seen as functioning independently, these collective nouns may be plural. My family have a lot of money.  (members of my family)Our team are working hard to win every game they play. (team members) ·        Some collective nouns in this group are:Family, team, crew, class, government, committee Some nouns have the same singular and plural form. They take singular or plural verb depending on the meaning. This species of monkeys lives only in India.There are many species of monkeys. ·        Some nouns in this group are:Species, series, deer, fish, sheep Expressions stating amount of time, money, weight, volume are plural in form but take a singular verb as in: Three weeks is a long time.Two hundred dollars is a lot of money. Some nouns look plural with –s but they take a singular verb. SciencesAbstract nounsDiseasesPhysicsMathematicsStatisticsEconomics NewsPoliticsEthics MeaslesMumps           Maths is found difficult by many students.Statistics requires complicated methods. Generic references with the require plural verb. The rich are not always happy.The young like to listen to loud music.The old hate loud music.The English are distant and the French are humorous. Note the use of foreign plurals. SingularPluralAnalysisThesisCrisisBasisParenthesisAnalysesThesesCrisesBasesParentheses CurriculumMemorandumDatumBacteriumMedium CurriculaMemorandaDataBacteriaMedia CriterionPhenomenon CriteriaPhenomena StimulusRadiusSyllabus StimuliRadiiSyllabi  Don’t forget that some common English words have irregular plurals. PluralSingularChildPersonChildrenPeople   A relative pronoun takes a singular or plural verb depending on which noun it modifies. Lisa is one of the students who have passed with an A.   (Many students passed with an A, Lisa is one of them.)Lisa is the only one of my students who has passed with an A. (Only Lisa passed with an A.)
Simple. If the subject is plural, then use the base/simple/singular form of the verb. If the subject is singular, then use the plural form of the verb.

Jan rides the bicycle
- the subject "Jan" is Singular so we use the S-form or plural form of the verb. (rides)

They dance gracefully.
- the subject "they" refers to many people so it means it is Plural, so we use the singular form of the verb. (dance)