Tefillin, also known as phylacteries, are a religious item worn by observant Jews during weekday morning prayers. These small black leather boxes contain four biblical passages written on parchment scrolls. The word tefillin comes from the Hebrew word תפילין, which means "prayer". However, there are a few other words that can be used as synonyms for tefillin, including shel rosh (קשר ראש), which means "head tefillin", and shel yad (קשר יד), which means "arm tefillin". Another word used for tefillin is "tefillah", which is the singular form of the word and also means "prayer". Tefillin are an important symbol of devotion and a physical way for Jews to connect with their faith.