Old Norse had a significant impact on the grammar of the English language. The most important change was the introduction of a new set of English third-person plural pronouns, they, them, and their. These replaced the earlier Old English forms: "'hi or hie' ('they/them'), hira or heora ('their, of them'), and him or heom ('to them, for them')." Another grammatical influence was the use of are, as a third-person plural of the verb 'to be.' This form had already been used in northern texts during the late Old English period but in Middle English, it eventually replaced the competing plural forms ''sindon and be.'