Tera- (T-)
Tera- (T-) :
A metric prefix meaning 1012, or one trillion. The prefix was derived from the Greek word for monster, teras. (Our words "terrible" and "terrific" have this same root.) The three prefixes mega-, giga-, and tera- thus mean something like "huge," "gigantic," and "monstrous," respectively. But also, and apparently by coincidence, the prefix tera- suggests the Greek tetra, meaning 4. This is significant because tera- is the fourth prefix, following kilo-, mega-, and giga-, in the list of SI prefixes for multiples of 1000n. This coincidence was exploited in defining the subsequent prefixes peta-, exa-, zetta-, and yotta-, corresponding to the powers n = 5 through 8 in 1000n, so that they suggest the Greek numbers penta, hexa, hepta, and okta for 5, 6, 7, and 8, respectively
