The word ‘Research’ is an uncountable noun that should always be used in a singular form, using the plural form is often counted as a writing mistake.

Pronunciation change

Noun change

Singular
research

Plural
researches

  1. The plural form of research; more than one (kind of) research.

Verb change

Plain form
research

Third-person singular
researches

Past tense
researched

Past participle
researched

Present participle
researching

  1. The third-person singular form of research.