Orderly, methodical, systematic, regular are comparable when they mean following closely a set arrangement, design, or pattern.
Orderly implies observance of due sequence or proper arrangement especially in the harmonious or careful disposition of persons or things or in obedience to the rules of conduct or behavior that guide disciplined persons or in keeping a place free from litter or confusion or in a scheme or system when all details stand in their proper relations, each playing its due part without interfering with that of any of the others.
Methodical implies the observance of an order that has been carefully worked out so that the steps to be followed are exactly known or the pattern that is accepted seems logical or inevitable under the circumstances.
Systematic comes close to methodical in ordinary use, but systematic, which always retains some notion of the ordered complex unity implied by the related noun (compare SYSTEM ), may be preferred when the stress is not upon the order followed but upon the integrated and ordered whole involved; thus, methodical study implies study pursued in regular increments according to a predetermined schedule while systematic study implies study pursued according to a scheme in which each increment leads logically to the next and the end result is exposure to an integrated block of information.
Systematic also may be used to suggest order in occurrence, in progression, and especially in repetition, still with some notion of an underlying system; thus, a systematic error is one that is inherent in a system of measurement or calculation and recurs whenever that system is used.
Regular, with its basic implication of conformance to a rule (see also REGULAR 1 ), may come very close to orderly. The term may imply steadiness or uniformity (as in following a schedule) or it may suggest occurrence and recurrence (as at fixed or stated intervals or in uniform amount).