1）代词what, which, who, none, some, any, more, most, all等词的单复数由其指代的词的单复数决定。例如：
All is right. 一切顺利。
All are present. 人都到齐了。
2）集体名词作主语时，谓语的数要根据主语的意思来决定。如family, audience, crew, crowd, class, company, committee等词后，谓语动词用复数形式时强调这个集体中的各个成员，用单数时强调该集体的整体。例如：
His family isn't very large. 他家成员不多。
His family are music lovers. 他家个个都是音乐爱好者。
但集合名词people, police, cattle, poultry等在任何情况下都用复数形式。例如：
Are there any police around? 附近有警察吗？
3）有些名词，如variety, number, population, proportion, majority 等有时看作单数，有时看作复数。例如：
A number of +名词复数+复数动词。
The number of +名词复数+单数动词。
A number of books have lent out.
The majority of the students like English.