Deductive reasoning takes place when someone narrows a thesis from general to specific. This contrasts with inductive reasoning, which takes place when one moves from detailed observations to broader generalizations.
A clear example of deductive reasoning is found in weather observations and actions that may occur as a result of the weather. One may observe that a thunderstorm with heavy rain is taking place in a certain location. One may also know from experience that outdoor sporting events are paused during thunderstorms for safety reasons. Based on the weather observation and prior experience, one may conclude that a specific outdoor baseball game is probably experiencing a weather delay if a strong thunderstorm is present near the stadium.