Definition of: ical

1. Like; pertaining to: ethical: used in adjectives derived from nouns in –ic, –ics.
2. With the same general meaning as –ic: comical; sometimes with extended or special meaning: economical. [<LL -icalis <-icus -IC + <-alis -AL]♦ –ic, –ical
In cases where both forms exist and do not differ greatly in meaning, there is no set rule governing usage. Euphony and past usage alone generally determine the choice of one form over the other.