| staid | great dignity |
| AD | Anno domini |
| BC | Before Christ |
| bicentennial | two hundredth anniversary |
| centennial | one hundredth anniversary |
| century | one hundred years |
| chronology | events in order |
| decade | ten years |
| generalization | broad conclusion |
| historian | studies the past |
| barometer | measures air pressure |
| bathysphere | sphere-shaped diving vessel |
| lens | transparent object that bends light |
| palpable | able to be touched |