From Middle English is, from Old English is, from Proto-Germanic *isti (a form of Proto-Germanic *wesaną (“to be”)), from Proto-Indo-European *h₁ésti (“is”). Cognate with West Frisian is (“is”), Dutch is (“is”), German ist (“is”), Old Swedish is (“is”).
The paradigm of "to be" has been since the time of Proto-Germanic a synthesis of four originally distinct verb stems. The infinitive form "to be" is from *bʰuH- (“to become”). The forms is and am are derived from *h₁es- (“to be”) whereas the form are comes from *iraną (“to rise, be quick, become active”). Lastly, the past forms starting with "w-" such as was and were are from *h₂wes- (“to dwell; reside”).
- Third-person singular simple present indicative form of be
i + -s.
- plural of i