Although tefillin is technically the plural form (the singular being tefillah), it is loosely used as a singular as well. The arm-tefillin, or shel yad, is placed on the upper arm, and the strap wrapped around the arm/hand, hand and fingers; while the head-tefillin, or shel rosh, is placed above the forehead.
Definition of declination. 1 : angular distance north or south from the celestial equator measured along a great circle passing through the celestial poles. 2 : a turning aside or swerving. 3 : deterioration moral declination. 4 : a bending downward : inclination.
Declination (delta): angular distance from the celestial equator (+=north, -=south). Right Ascension (alpha): angular distance along circles parallel to the equator. Define zero point to be the vernal equinox, the point where the Sun's position crosses the celestial equator as it moves north. Right ascension increases going eastward. Dec is measured in degrees, minutes of arc, seconds of arc, or decimal degrees.