(Latin: distrahere, draw away)
A drawing away of the mind from one point or course to another or others.
Here we consider distraction as it is wont to happen in prayer and in the administration of the sacraments.
Distraction is voluntary, when the want of attention is due directly or indirectly to an act of will; involuntary when it occurs through no fault on the part of the one distracted.
Voluntary distractions at prayer are venially sinful, because they are a manifestation of irreverence toward God.
Involuntary distractions are not sinful.
Distractions, it need hardly be noted, are destructive of mental prayer, which consists in the fixing of the mind and the heart upon some sacred truth.
Distractions do not completely vitiate vocal prayer, though they diminish its perfection, provided always that the original intention of praying was present.
Prayer has a threefold effect: it is meritorious, and occasional distractions do not destroy this quality; it has impetratory power, and this too it retains in spite of distractions; it refreshes the mind spiritually, and for this effect attention is a necessary condition.
Distraction and mind-wandering, on the part of the minister of a sacrament, do not invalidate the sacrament.
Provided he has the right intention, and fulfils the essentials of the external rite proper to each sacrament, no matter how much his attention may wander, his act is a human one, and the sacrament is valid.
New Catholic Dictionary