Subject-Verb Agreement

Verbs always agree with the subject noun in a sentence:
always go to work early.
She always goes to work early.
We are old
 house is old.
However, there are many types of noun and noun phrase in English, and it can be difficult to know if a particular noun takes a singular verb (such as DOES / HAS / AM / IS ) or a plural verb (DO / HAVE / ARE). Have a look below for some commonly difficult nouns:

1. When singular and plural are the same.

The species is on the brink of extinction.’ (It…)
The species are on the brink of extinction.’ (They…)
Here the noun ‘species’ does not change form to show a plural, even if the meaning changes. In this case, be careful about whether you are taking in the singular or plural meaning and make sure to change the verb. Other examples include: economics, sheep, politics, headquarters, series and fish (which has an alternative plural).
The sheep is herded by the sheepdog into the farmer’s van’ (It…)
The sheep are herded by the sheepdog into the farmer’s van’ (They…)
Their country’s politics are a mystery to me’ (Their opinions)
Politics is a mystery to me’ (The subject)
The BBC’s new TV series is excellent’ (It..)
The BBC’s new winter season TV series are excellent’ (They…)

2. Nouns with no plural. ( Subject-Verb Agreement)

The news about the king’s death has been reported around the world.’ (It…)
Many English learners will know that English has countable and uncountable nouns. When you want to show a plural countable noun, you use a ‘s’ e.g. a hat / 3 hats. Uncountable nouns have no plural and always use a singular verb. But, ‘news’ is a noun that is uncountable AND ends in an ‘s’, which can lead many learners to use the wrong verb form. Here are some more examples: school subjects, such as mathematics, gymnastics and physics; Games, such as dominos and darts and the disease: measles.
Mathematics is a hard subject’ (It…)
‘What does measles do?’ (It…)
Dominos has been around for almost a thousand years’ (It…)
“Subject-Verb Agreement ”

3. Nouns with no singular

The police are coming! The police are coming!’
Some nouns in English are collective. This means that they represent a group or number of objects together. In many cases, these nouns are considered to be plural all the time since they are collections of single pieces kept together. Because of this, they take a plural verb and have no singular noun form. Here are some more examples: staff, congratulations, cattle, thanks and fishes (an alternative plural which means the different species of fish which are in the same place).
The staff are unhappy with the wage cut’ (They…)
Congratulations are due to you on your birthday’ (They…)
‘The supermarket has many fishesThey have been organised according to type.’
This also applies with ‘pair nouns’, i.e. nouns where two things are joined together. Examples of these are: glasses, scissors, tweezers, trousers, heaphones and tights.
My jeans don’t fit anymore!’ (They…)
Are my glasses in the kitchen?’ (They…)
Tights were fashionable as far back as Henry VIII’s time!’ (They…)
Finally, in English we can combine the definite article THE with an adjective to create a group noun meaning ‘all of..’. This is common for nationalities. They also take a plural verb.
The British are coming. The British are coming.’
The rich have the most to lose’
The sick have suffered enough’