| A | B |
|---|
| decade | a period of 10 years |
| century | a period of 100 years |
| age | a long period of time marked by a single cultural feature |
| era | a long period of time marked by great events, developments, or figures |
| ancient | very old, or from a long time ago |
| circa or c. | a word used to show that historians are not sure of an exact date; it means about |
| B.C. | before the birth of Christ |
| A.D. | after the birth of Christ |
| BCE | another way to refer to BC dates; it stands for "before the common era" |
| CE | another way to refer to AD dates; it stands for "common era" |
| history | study of the past |
| prehistory | time before there was writing |
