He made a conscientious effort to get the work finished.
He made a conscientious decision to buy his daughter a computer
Some interesting info here on American and Non-American varieties of English - Seems Pedro's point was a valid one!
Defence vs. Defense
Defence and defense are different spellings of the same word. Defense is preferred in American English, and defence is preferred in all other main varieties of English, including Australian, British, and Canadian English. The spelling distinction extends to most derivatives of defence/defense, includingdefences/defenses and defenceless/defenseless. But the words defensive, defensiveness, and defensivelyhave an s everywhere.
Though defense is now the American spelling, it is not American in origin. The OED and Google Books reveal examples of the spelling from as long ago as the 1300s, many centuries before the United States existed. That spelling continued to appear a fraction of the time through the 19th century, when it was taken up by American writers. Today, to the chagrin of those who dislike American English, the spelling is gaining ground throughout the English-speaking world.