Singular &quot;they&quot;, for the purposes of grammatical agreement, is indistinguishable from plural &quot;they&quot;, in much the same way that singular &quot;you&quot; acts like plural &quot;you&quot;.  The distinct singular 2nd person pronouns and verb forms are now archaic and obsolete.<p>You wouldst not match the verb form associated with &quot;thou&quot; when using the singular &quot;you&quot;.  When anyone does, they sounds wrong to the ear of a native speaker.<p>(The above is intentionally wrong for illustrative purposes.)