Many adjectives end in either '-ic' or '-ical'.
Examples of Adjectives ending in '-ic':
The boys are very athletic and play a variety of sports
I didn't realize you were so energetic! You've completed 10 exercises in the last hour.
His writings were very prophetic and some think show the way of the future.
Many feel that the only valid way to learn is the scientific approach.
Examples of Adjectives ending in '-ical':
We had a magical evening at the concert.
His political use of the military was diabolical.
I wish she weren't so cynical. I don't know whether I can believe anything she says.
You Timothy is quite musical and plays the piano well.
An extension of the adjective ending '-ical' is the adjective ending in '-logical'. These adjectives tend to be used with scientific and medical related terms.
Examples of Adjectives ending in '-logical':
The psychological study of patients has led to many helpful discoveries.
The cardiological unit of the hospital has saved many lives.
The chronological listing of each King's reign can be found on page 244.
Many feel that an ideological approach to our political problems will not solve anything.
There are a few cases in which both adjective endings are used with slight changes in meaning. Here are some of the most common:
economic / economical
economic = relating to economics and finance
economical = money saving, frugal
The economic picture looks pretty depressing for the next few quarters.
It's economical to reuse your banana peels as compost.
historic / historical
historic = famous and important
historical = dealing with history
The historic Battle of the Bulge was fought in Belgium.
The historical significance of Da Vinci's writings was discussed in Peter Gould's essay.
lyric / lyrical
lyric = relating to poetry
lyrical = resembling poetry, musicality, etc.
Lyric poetry reading can help you find the music of everyday language.
His lyrical approach to scientific writing help to popularize the subject.