caéis
Caéis is the second-person plural present indicative form of the Spanish verb caer, meaning you all fall or you all are falling. It is used with the informal vosotros subject pronoun, which is standard in Spain and in some other regions, but not common in much of Latin America where ustedes is used instead.
Caer is an irregular verb in some present forms; its yo form is caigo, and its third-person
Usage varies by region. In Spain and some communities that use vosotros, caéis is routinely heard in