The Greek words from which "catechism" is derived, according to their common signification, mean to sound, to resound, to instruct by word of mouth, and to repeat the sayings of another. More properly, however, katecheo means to teach the first principles and rudiments of some particular doctrine. As applied to the doctrine of the church and as understood when thus used, it means to teach the first principles of the Christian religion, in which sense it occurs in Luke 1. 4, Acts 18. 25, Gal. 6. 6, etc. Hence, catechisation in its most general and comprehensive sense, means the first brief and elementary instruction which is given by word of mouth in relation to the rudiments of any particular doctrine; but, as used by the church, it signifies a system of instruction relating to the first principles of the Christian religion, designed for the ignorant and unlearned.