Certain singular nouns which are uncountable in English are countable in many other languages. Examples are: hair, baggage, furniture, advice etc.
- Her hair is very thick. (NOT Her hair are very thick.)
- My baggage has been stolen. (NOT My baggages have been stolen.)
When two singular subjects are joined by and, the verb is normally plural.
- Alice and Peter are going to get married.
But note that some phrases with and are treated like single ideas.
- ‘Romeo and Juliet’ is my favorite play. (NOT Romeo and Juliet are my favorite play.)
Two subjects connected by as well as, together with or a similar expression are followed by a singular verb if the first subject is singular.
- The manager, as well as his colleagues, believes in a tough financial policy.
When two subjects are joined by or, the verb is usually singular if the second subject is singular, and plural if it is plural.
- Grapes or a melon is suitable.
- A melon or grapes are suitable.
When two singular subjects are joined by neither…nor, the verb is singular in a plural style, but is usually plural in an informal style.
- Neither Mary nor her brother has arrived. (Formal)
- Neither Mary nor her brother have arrived. (Informal)