late 14c. as a term in astronomy, from Old French depression (14c.) or directly from Latin depressionem (nominative depressio), noun of action from past participle stem of deprimere to press down, depress (see depress). Attested from 1650s in the literal sense; meaning dejection, depression of spirits is from early 15c. (as a clinical term in psychology, from 1905); meteorological sense is from 1881 (in reference to barometric pressure); meaning a lowering or reduction in economic activity was in use by 1826; given a specific application (with capital D-) by 1934 to the one that began worldwide in 1929.
Vertical Timeline. Use these Vertical Timeline slides to present a timeline, series of events, or linear process. This slide set is a variant of the Timeline slide set. You can present anywhere from five stages to ten stages by selecting the appropriate slide from this slide set. Please refer to the Timeline for more information.
Horizontal Undulatory Progression or Lateral Progression for short. This method of movement is accomplished by the snake lashing it's body back and forth causing lateral waves that force longitudinal motion. To put it another way: They go forward by moving sideways. So imagine a person jumping in diagonal leaps.